1. t r nh o t occGIO TRNH AN TON H THNG THNG TIN1

2. MC LC MC TRANG1. LI TA ........................................................................................................... 32. GII THIU V M UN MN HC................................................................ 53. S QUAN H THEO TRNH T HC NGH............................................. 64.CC HNH THC HC TP CHNH TRONG M UN/MN HC ................... 85. BI 1: PHN TCH CC NGUYN NHN DN N MT AN TON TRONG H THNG THNG TIN ................................................................................... 96.BI 2: LU TR H THNG THNG TIN TRN CC THIT B LU TR .... 177.BI 3: VIRUS TIN HC V CCH PHNG CHNG ......................................... 498.BI 4: MT S BIN PHP AN TON CHO CC H THNG MY TNH ...... 589.BI 5: MT S PHNG THC M HO V GII M D LIU ................... 6810.BI 6: XY DNG K HOCH BO V H THNG THNG TIN TRNMY TNH ........................................................................................................ 8011.TI LIU THAM KHO ..................................................................................... 1002 3. BI 1Tn bi: PHN TCH CC NGUYN NHN DN N MT AN TON TRONG H THNG THNG TINGii thiu :Khi ni n an ton thng tin (ATTT), iu u tin ngi ta thng ngh n l xy dngtng la (Firewall) hoc mt ci g tng t ngn chn cc cuc tn cng v xmnhp bt hp php. Cch tip cn nh vy khng hon ton ng v bn cht ATTT khngn thun ch l s dng mt s cng c hoc mt vi gii php no m m boATTT cho mt h thng cn c mt ci nhn tng qut v khoa hc hn.Mc tiu thc hin:- Xc nh tt c nhng nguyn nhn dn n d liu trn my tnh b mt- Phn tch nhng nguyn nhn a n vic r r thng tinNi dung chnh:1.1 Vai tr quan trng ca thng tin trong mt n v.Vy an ton thng tin l g?Khng th m bo an ton 100%, nhng ta c th gim bt cc ri ro khng mongmun di tc ng t mi pha ca cc lnh vc hot ng kinh t x hi . Khi cc t chc,n v tin hnh nh gi nhng ri ro v cn nhc k nhng bin php i ph v ATTT, hlun lun i n kt lun: nhng gii php cng ngh (k thut) n l khng th cung cp s an ton. Nhng sn phm Anti-virus, Firewalls v cc cng c khc khng th cungcp s an ton cn thit cho hu ht cc t chc. ATTT l mt mt xch lin kt hai yu t:yu t cng ngh v yu t con ngi.1. Yu t cng ngh: bao gm nhng sn phm nh Firewall, phn mm phng chng virus,gii php mt m, sn phm mng, h iu hnh v nhng ng dng nh: trnh duytInternet v phn mm nhn Email t my trm.2. Yu t con ngi: L nhng ngi s dng my tnh, nhng ngi lm vic vi thng tinv s dng my tnh trong cng vic ca mnh.Hai yu t trn c lin kt li thng qua cc chnh sch v ATTT.Theo ISO 17799, An Ton Thng Tin l kh nng bo v i vi mi trng thng tin kinh tx hi, m bo cho vic hnh thnh, s dng v pht trin v li ch ca mi cng dn, mit chc v ca quc gia. Thng qua cc chnh sch v ATTT , lnh o th hin ch vnng lc ca mnh trong vic qun l h thng thng tin. ATTT c xy dng trn nn tngmt h thng cc chnh sch, quy tc, quy trnh v cc gii php k thut nhm mc chm bo an ton ti nguyn thng tin m t chc s hu cng nh cc ti nguyn thngtin ca cc i tc, cc khch hng trong mt mi trng thng tin ton cu. Nh vy , vi vtr quan trng ca mnh , c th khng nh vn ATTT phi bt u t cc chnh schtrong con ngi l mt xch quan trng nht. 3 4. Con ngi khu yu nht trong ton b qu trnh m bo an ton thng tin . Hu nhphn ln cc phng thc tn cng c hacker s dng l khai thc cc im yu ca hthng thng tin v a phn cc im yu rt tic li do con ngi to ra. Vic nhn thckm v khng tun th cc chnh sch v ATTT l nguyn nhn chnh gy ra tnh trng trn.n c l vn s dng mt khu c quy nh rt r trong cc chnh sch v ATTTsong vic tun th cc quy nh li khng c thc hin cht ch. Vic t mt mt khukm cht lng, khng thay i mt khu nh k, qun l mt khu lng lo l nhng khuPhng php nh gi cht lng h thng ATTTC l khng mt v lnh o no dm khng nh ni b cng ty l thc s an ton v tincy. Trong bi cnh nn kinh t th trng nh hin nay, s canh tranh din ra gay gt thmch gia cc nhn vin trong ni b cng ty: tranh dnh khch hng , mc ch thng tinhoc cc mc ch khng lnh mnh khc. mt s t chc, li dng s lng lo trongqun l v ATTT, nhn vin c nhng hnh vi bt lng nh ly cp thng tin mt, chimot ti khon khch hng , n cp tin thng qua h thng tn dng Theo thng k,khong 70% cc ri ro v ATTT l xut pht t ni b trong t chc. Mt trong nhng cuhi lun c t ra trc cc nh lnh o v cc nh qun tr thng tin l: H thng thngtin ca t chc an ton n mc no? Cu hi ny l mi quan tm ln nht v cng lvn nhy cm nht trong cc khu qun l h thng thng tin.Tr li cu hi ny tht khng n gin nhng khng phi l khng c cu tr li. giip vn trn, ch yu da vo hai phng php nh gi ATTT nh sau:+ Phng php nh gi theo cht lng ATTT ca h thng bng cch cho im.V d: hthng t 60/100 im hoc 60%+ Phng php nh gi theo s lng thit b - cng ngh bo mt.Trong thc t , phng php nh gi theo cht lng l phng php duy nht nhgi mc an ton ca cc ti nguyn trong h thng thng tin. Vit Nam, vic nh giATTT theo cht lng l hon ton mi. Ngi ta d ng nhn vic trang b mt cng cATTT nh (Firewall, Anti-virus) l m bo c ATTT cho h thng. Cht lng ATTTphi c nh gi trn ton b cc yu t m bo tnh an ton cho h thng t t chc,con ngi, an ninh vt l, qun l ti nguyn n vic s dng cc cng c k thut. Nicch khc, cht lng ATTT c nh gi trn c s thc thi cc chnh sch v ATTTtrong h thng. Cc chnh sch ny c chun ho v c cng nhn l cc tiu chunv ATTT p dng trn phm vi ton th gii.Phng php nh gi theo s lng khng c s dng.Tiu chun nh gi v cht lng ATTT.Vic nh gi mc ATTT ca cc t chc thng c tin hnh theo kinh nghim vda trn cc quy nh mang tnh cm tnh , cc b ca t chc m khng tnh n cctiu chun c th gii cng nhn . Vi nm trc y, Vin Tiu chun ca Anh (BSI)cng vi mt s t chc thng mi khc nh Shell, National Westminster Bank, MidlandBank nghin cu v xut mt tiu chun v ATTT. n nm 1995, tiu chun nyc cng nhn l tiu chun quc gia v qun l ATTT - BS7799. Tiu chun ny c lpvi m hnh hot ng ca cc cng ty. Lnh o cng ty, cc CSO/CIO da trn cs cc tiu chun ny thit lp cc chnh sch ATTT cho n v mnh. Ngay sau khi rai, BS7799 c s dng 27 nc bao gm cc nc thuc khi lin hip Anh cng 4 5. nh mt s quc gia khc nh Thy S, H Lan... n nm 2000, T chc tiu chun thgii ISO trn c s BS7799 xy dng tiu chun ISO 17799 v tiu chun ny tr thnhtiu chun quc t v qun l cht lng ATTT (ISO/IEC 17799). Tnh n thng 2/2005 c khong hn 1000 t chc nhn chng ch ISO 17799 trong c Hitachi, Nokia,Nhng phn c bn ca ISO 17799:1. Chnh sch chung2. An ninh nhn s (Personel Security)3. Xc nh, phn cp v qun l ti nguyn (Asset Identification, Classification & Control).4. An ninh vt l (Physical Security).5. An ninh t chc (Security Organization).6. Qun tr IT v mng (IT operations and network management).7. Qun l truy cp v cc phng php (Access control & methods).8. Pht trin HT v bo tr (System development & maintenance).9. Tnh lin tc trong kinh doanh v k hoch phc hi sau s c (Bussiness Continuty &Disaster Recovery Planning)10. Ph hp h thng vi cc yu t v lut php, o c (Low, Inestigation and Ethics).Hnh 1.1 Nhng phn c bn ca ISO 17799Chnh sch v an ton thng tin c t chc theo m hnh kim t thp.Cch t chc nygip cho cc nh lnh o qun l cht lng an ton thng tin mt cch khoa hc v hiuqu.Trn nh kim t thp m t cc chnh sch c p dng trong t chc .Ti sao ta phithit lp chnh sch ny ? Phm vi v i tng tc ng ca chnh sch? . Khng c mtchnh sch p dng chung cho mi n v. Trong mt t chc c nhiu b phn , tng bphn li c chc nng nhim v khc nhau, tnh cht v cch t chc thng tin cng khcnhau .B phn kinh doanh c m hnh thit k h thng ring vi c s d liu mang cth kinh doanh , b phn sn xut ,b phn nghin cu cng c cu trc h thng v c sd liu ca ring mnh .Trnh nhn thc v an ton thng tin cng rt chnh lch . Chnhv vy khi thit lp cc chnh sch ,nh qun l cn xc nh r mc ch ca chnh schc thit lp , i tng thc thi , phm vi tc ngLp th hai trn m hnh m t cc quy tc ,quy nh thc thi cc chnh sch . thc hincc chnh sch ta phi lm g ? H thng cc quy tc ATTT c th hin trn 10 lnh vcln bao hm cc quy nh t t chc , con ngi , an ninh vt l n cc cng c k thut anton thng tin .Cc quy tc c xy dng trn m hnh IT chun ca t chc v th hin 5 6. c tnh c th ca t chc .Thng qua vic thc thi cc quy tc , c th nh gi chtlng an ton thng tin ca mt t chc thng qua kim ton (Audit) .Lp th ba l lp cui cng ca m hnh . y l cc quy trnh , cc gii php h tr thc thicc quy tc , quy nh trn.N tr li cho cu hi lm nh th no thc thi cc quy nhtrn ? Cc nh qun tr an ton thng tin (CSO) cng cc qun tr IT thit lp cc quy trnhny v ph bin n mi nhn vin trong t chc ,v d Quy trnh thay i mt khu,Quytrnh ci t cc chng trnh dit virut ,chng cc chng trnh c hi v.v.Cc quy trnhny c th lin quan n nhiu chnh sch v i tng s dng khc nhau.Vic p dng ISO 17799 em li li ch g cho t chc?Vic p dng cc tiu chun v ATTT theo ISO 17799 lm tng nhn thc cho i ng cnb nhn vin v ATTT. Xy dng mt mi trng an ton, c kh nng min dch trc ccri ro, gim thiu cc nguy c do con ngi gy ra. Tiu chun ISO 17799 ra nhngnguyn tc chung trong qu trnh thit k , xy dng h thng thng tin mt cch khoa hc,gip cho vic qun l h thng tr nn sng sa, an ton, minh bch hn. Chng ta xydng mt bc tng ngi an ton (Secure People Wall) trong t chc. Mt mi trngthng tin an ton, trong sch s c tc ng khng nh n vic gim thiu chi ph vt chtu t cho ATTT vn d rt tn km. V lu di, vic nhn c chng ch ISO 17799 l mtli khng nh thuyt phc vi cc i tc, cc khch hng v mt mi trng thng tin anton v trong sch . To iu kin thun li cho s hi nhp mt mi trng thng tin lnh1.1 Vn o to ngun nhn lcTheo IDG vo khong nm 2006 s bng n mt ngh mi trong lnh vc IT ngh an tonthng tin.Chc danh CSO (Chief Security Officer) tr nn quen thuc trong lnh vc IT.Cp nht v nng cao kin thc v ATTT v nhn thc v vai tr ca n trong h thng IT lmt iu rt quan trng v cp bch v xt cho cng hnh ng ca con ngi l yu tquyt nh . Mc d ATTT c bit n rng ri nhng yu t con ngi thng t ccc t chc quan tm n. i vi nhng nh qun tr, h cn mt chnh sch an ton vmt chng trnh nhn thc cng nh nh gi cht lng v ATTT nhng tic rng hinnay cha c nhiu gii php thc s quan tm vo vn lm sao tng cng s vngchc cho mi lin kt vn d rt yu t ny trong mt xch ATTTHin nay, mt s doanh nghip ti Vit Nam c s chuyn bin tch cc trong vn nhn thc v ATTT. H sn sng u t ngn sch o to ngun nhn lc nhm to nntng vng chc v nhn thc v kin thc ATTT cho i ng nhn vin ca doanh nghip.in hnh l nh: S Khoa hc v Cng ngh ng Nai, Cng ty Bo him Bo Minh,Fujitsu Vietnam, Ngn hng Chu ...Bn cnh vn cn nhiu doanh nghip nht l cc doanh nghip va v nh vn chatip cn v hiu ht tm quan trng ca vic thit lp cc chnh sch v ATTT v qun l tiuchun cht lng ATTT theo ISO 17799 thc s vn cn xa l v mi m i vi h.1.2 Phn tch nhng nguyn nhn a n thng tin trn a b mt6 7. -RAID controller b hng.( Redundant Array of Independent Disks)-Ngi dng v hoc khng lu thay a mi khi a b h,gy ra s h hng ca a khc trong cng mt RAID.-D liu RAID registry trong b nh b hng.-Tng v tt in p t ngt, thm ha t nhin.-Li do ngi s dng, v tnh xa thng tin hoc li phn mm ca a cng.-Ngi s dng reconfigure dung lng a cng sai.-Virus tn cng hoc ngi s dng v tnh nh dng sai mt a cng trong h thngRAID.RAID l ch vit tt ca Redundant Array of Independent Disks. Ban u, RAID c sdng nh mt gii php phng h v n cho php ghi d liu ln nhiu a cng cng lc. Vsau, RAID c nhiu bin th cho php khng ch m bo an ton d liu m cn gipgia tng ng k tc truy xut d liu t a cng. Tuy nhin vic mt d liu t RAIDkhng phi l chuyn khng c, v ngi s dng thng cm thy ch quan v RAID nnthiu s sao lu d liu cn thit.Cc loi RAID:RAID 0:Cn c gi l "Striped Volume", n c s dng gia tng s truy cp d liu. Trongcu hnh RAID 0 ny n c th h tr t 2 disks cho n 32 physical disks, d liu c chiau ra trn cc disks, v n lm vic nh l mt logical khi (Volume). Mc d n c gil RAID (Redundancy Array of Inexpesive Disk), nhng tht s trong cu hnh ny n khngc "Redundancy". Vi cu hnh RAID ny, nu mt trong hai disk ca khi RAID ny rt ths truy cp d liu vo khi ny s b mt ht.RAID 1:Cu hnh RAID ny cn c gi l cu hnh "Khi Phn Chiu" (Mirrored Volume), trongcu hnh ny d liu c mirrored gia hai physical disks cho mc ch redundancy. ViRAID 1 tt c nhng d liu c vit v volume th nht trong khi mirrored th n sc vit v volume th hai trong khi ny bi fault tolerant driver ftdisk.sys. D liu v vyc m bo an ton hn Raid 0.RAID 1+0:L s kt hp ca Raid 0 v Raid 1 vi s hin din ca Fault Tolerance a ra mt hthng hon ho c u im ca c hai loi Raid,s nhanh nhy ca Raid 0 v s an tonca Raid 1.Tuy nhin chi ph cho mt h thng ny kh t v phi cn t nht 4 a cng c th thit lp.RAID 5:RAID 5 thng c bit nh l "Stripe set with parity". Trong cu hnh RAID ny, n sdng t nht l 3 v nhiu nht l 32 physical disks, khng ch ring d liu c phn phiu trn cc disk m nhng thng tin lin kt cng c phn phi trn cc disks, chcchn rng d liu s c cu thnh li nu mt trong nhng disk c lp b rt. Ni nghn l nu bt k disk no trong khi ny b rt th bn c th thay i mt disk mi v n st ng cu hnh li (Rebuild) tt c nhng d liu b mt.Cc loi RAID khc:Ngoi cc loi c cp trn, bn cn c th bt gp nhiu loi RAID khc nhngchng khng c s dng rng ri m ch gii hn trong cc h thng my tnh phc vmc ch ring, c th k nh: Level 2 (Error-Correcting Coding), Level 3 (Bit-InterleavedParity), Level 4 (Dedicated Parity Drive), Level 6 (Independent Data Disks with DoubleParity), Level 10 (Stripe of Mirrors, ngc li vi RAID 0+1), Level 7 (thng hiu ca tpon Storage Computer, cho php thm b m cho RAID 3 v 4), RAID S (pht minh catp on EMC v c s dng trong cc h thng lu tr Symmetrix ca h). Bn cnh cn mt s bin th khc, v d nh Intel Matrix Storage cho php chy kiu RAID 0+1 vich 2 cng hoc RAID 1.5 ca DFI trn cc h BMC 865, 875. Chng tuy c nhiu imkhc bit nhng a phn u l bn ci tin ca cc phng thc RAID truyn thng.1.3 Phn tch nhng nguyn nhn a n r r thng tin trn my tnh7 8. R r thng tin trong doanh nghip qua th nh:Thng thng, mi ngi c th dng nhng thit b kiu ny t do trong gi lm vic mkhng cn s cho php ca cp trn. Th nh c nhn vin mang i khp phng v cmvo cng USB sao chp bi ht c sn trong my tnh ca ngi khc.Tuy nhin, s lng lo ny s tip tay cho bt c ai cng c th lu ton b thng tin trnmy tnh no vo trong th nh dung lng ln mt cch c ch ht sc nhanh chng.R rng, trong khi nhiu hng tiu tn c ni tin bo v mnh thot khi nguy c tvirus, spyware, spam..., th h li qun li cnh bo mun thu ca cc chuyn gia bo mtrng him ha ln nht bao gi cng nm chnh bn trong mi cng ty.Mt s hng thc hin nhiu bin php ngn cn vic sao chp d liu t my tnhvo th nh v my nghe nhc, nhng cm dng nhng thit b ny l v l v s khng ththc hin c trn thc t. Do , cc cng ty cn trang b nhng cng c, ng dng tinhvi c th ghi li hot ng ca ngi trong mng ni b trnh tht thot d liu, r rthng tin hoc nhim virusR r thng tin trong doanh nghip qua my tnh xch tay:Trong nhiu trng hp, nhn vin mang thng tin ca cng ty ra khi vn phng bngchic laptop. Tuy nhin, h khng bo v s an ton cho chng v t ra ngi ngn khi dngcc c ch m ha nh ci password cho my v cc tp tin. Alan Paller, Gim c Hcvin SANS chuyn nghin cu vn bo mt my tnh, gii thch l do l nu h qun mtkhu th s khng m c tp tin v cc thao tc ny c v lm chm cng vic ca h.iu ny khin cc nh sn xut my tnh lu tm v bt u tch hp c ch m havo sn phm. V d nh h iu hnh Windows Vista ca Microsoft s gip ngi s dngd dng m ha d liu ca mnh hn.Cc cng ty c lng ln nhn vin di ng cng bt u quan tm n iu ny. V d nhhng t vn ti chnh Ernst & Young vi 30.000 my tnh xch tay phc v cho cng ty angm ha tt c ni dung trn my sau v thng tin v 243.000 khch hng ca h cha trongmt chic laptop b nh cp, bao gm tn, a ch, thng tin th tn dng.1.4 Mt s bin php khc phc.Cc chuyn gia a ra li khuyn vi cc bc sau:1. Phi kim sot d liuChc chn bn khng th no kim sot c thng tin nhy cm hay thng tin bn quyntrn mng nu ngay c v tr ca chng nm u bn cng khng bit.D liu nhy cm ca mt t chc thng c phn phi rng ri qua mng ni b. Dliu quan trng thng khng ch nm trong c s d liu (CSDL) m c khi c trong thin t, my tnh c nhn v i khi ng vai tr nh kiu i tng d liu trong cng Web.Thng tin nhy cm cng c nhiu kiu khc nhau, nh m s th tn dng, m s bo mtx hi (CMT, th sinh vin). Cc b mt thng mi c th c tm thy trong nhiu loifile, vn bn khc nhau theo kiu thng tin lin h khch hng, hp ng, chi tit k thutpht trin sn phm.Trin khai quy nh kim sot cho tt c cc loi d liu thng khng mang li hiu qu vkhng thc t. Thay vo , hy phn loi tng lp d liu v chn ra quy nh kim sotph hp nht cho mi loi. Bn cng c th s dng mt s cng c r sot mng t ngv xc nh v tr d liu nhy cm. Nhiu hng cung cp cc loi cng c ny nhReconnex, Tablus, Websense. S lng sn phm ca cc hng ngy cng phong ph.Nhiu trong s c th phn tch d liu thnh nhiu loi khc nhau, da trn quy nh docng ty t ra.2. Gim st ni dung di ngKhi cc cng ty s dng Website trong giao dch thng mi v lin kt vi nhiu mng 8 9. thuc v i tc, nh cung cp hay khch hng th vn sng cn l phi theo di c cig ang din ra, ang tri ni qua cc mng. Gim st ni dung l phn c s ct li trongchin lc bo v d liu ca nhiu cng ty. Vi qu nhiu im ra mng cho d liu, iuquan trng nht l phi gim st c lu lng mng.Tt c cc hng sn xut nh Vericept Corp., Vontu Inc., Oakley Networks Inc., Reconnexv Websense u bn mt lot sn phm c chc nng kim tra, r sot e-mail, trnh tinnhn tc thi (Instant Messaging), h thng chia s file peer-to-peer, qu trnh post Web vc cc website FTP nhm pht hin v tm kim hot ng xm phm d liu hay vi phmquy tc t ra trong cng ty. Cc cng c ny c t gn cng vo mng v c thit k a ra cnh bo khi pht hin gi d liu ng ng. Nhiu sn phm c th c dng thc p cc hot ng nh loi b hay m ho d liu khi d liu c truyn ra ngoi.V d, mt trong s l cc cng c lc ni dung, cho php bn thy c tt c nhng gang n hoc ang ra ngoi mng. Nh Bowers ca cng ty hng u Wyeth nhn xt:Chng ti gim st c tt c cc cng v tt c giao thc truyn ti ni dung khi hngny trin khai cng c lc ni dung.3. Hy mt n c s d liu c cha nhng thng tin qu bu ca cng tyng dng li vic bit ai ang truy cp c s d liu. Bn cn cn phi phi bit khi no, u, nh th no v ti sao h li thc hin truy cp ny. Nhiu cng c h tr c xydng, cho php cc cng ty gim st truy cp hay cc hot ng trn c s d liu. Bn cth dng sn phm ca Imperva Inc., Guardium Inc., Application Security Inc. v LumigentTechnologies Inc. Chng c thit k nhm mc ch gip bn bit ngi dng hay adminno ang lm vic trn c s d liu vi c quyn truy cp, hay chnh sa, copy, xo,download s lng ln tp hp cc file, hoc a ra cc cnh bo khi ai c gng thchin mt trong cc hot ng trn. Cc sn phm ny cng cung cp du vt kim tra kh rrng theo di khi c ngi vi phm quy nh ca doanh nghip.M ho d liu nhy cm trong c s d liu l mt phng php khc ng xem xt.4. Gii hn c quyn ngi dngHu ht cc cng ty u cung cp nhiu c quyn cho ngi dng hn so vi cn thit. l nhn nh ca Amichai Shulman, gim c cng ngh ca Imperva. Gim st truy cp dliu cc k quan trng ca ngi dng v theo di truy cp khng xc nh vi d liu mc nguy him cao l nhng bc khng th thiu.To quy nh truy cp nhm gii hn c quyn mng ca ngi dng mt cch cht ch.Ch cho php truy cp lp d liu tng ng cn thit cho cng vic ca tng kiu ngidng, ng thi thit lp cc iu khin nhm bt buc nhn vin trong cng ty phi tun thquy nh ni b xy dng. V d, a ra cnh bo khi ai vn bnh thng ch lm vicvi 10 tp ti liu mi ngy, t nhin bt u truy cp s vi lng ln hn.Vic a ra quyt nh iu khin truy cp cho thnh vin ni b v ngi ngoi l kh ngin, Matt Kesner - gim c cng ngh ca Fenwick & West LLC, hng lut c tr s tiCalifoocnia (M) khng nh. Nhng i khi ngi bn ngoi li cn truy cp hp php dliu ca doanh nghip vi s lng ngang bng hoc thm ch ln hn nhu cu ca nhnvin ni b. V d, cc mng Extranet client ca Fenwick & West ang c s dng thngxuyn bi khch hng hp tc vi nhn vin u quyn ca hng. i khi, ngi dng bn 9 10. ngoi hng th vi d liu ca doanh nghip hn nhiu so vi ngi trong ni b cng ty.5. Quan tm ti cc im cuiS pht trin nhanh chng ca th trng thit b di ng nh laptop, cc my xch tay khc,th nh USB hay my nghe nhc iPod ngy cng to iu kin cho nhng k c xutrong ni b cng ty n cp d liu d dng hn. Cc cng ty cn phi pht trin hot ngiu khin v gim st tp trung ho. Trong , thit b phi c gn vo mng v h thngdoanh nghip, quy nh r d liu no c download, upload hay lu tr ti u. Thc hinc cc cng vic ny l c mt thch thc. Nhng bn khng cn qu lo lng, v mt ssn phm ca cc hng nh Code Green Networks Inc., ControlGuard Inc. v SecureWaveSA s gip bn d dng hn khi tin hnh cc hot ng mong mun.Trc y, c rt t cng ty t cc kim sot hiu qu vo ng ni cn thit cho phph gim st h thng ni b mt cch cht ch v theo di c qu trnh di chuyn haytruyn vn ca d liu, Alex Bakman - gim c iu hnh ca Ecora Software Corp khngnh. iu c ngha l hot ng ph hoi tng din ra khng kn khng trng trongsut thi gian di.6. Tp trung ho d liu bn quyn tr tui vi mt cng ty ln, vic bo v bn quyn tr tu ri rc trn nhiu h thng l iukhng th. Do , lu tr cc d liu ny trong mt h thng th vin ti nguyn tp trungho bt c khi no c th l bin php an ton v tin li trong trong bo mt cng nh chias thng tin.Thng thng, ngi ta t tt c trng vo trong mt r, Ira Winkler - chuyn vin t vnbo mt t do v ph trch chuyn mc Computerworld.com v von. Nhng trong trnghp ny, bo v mt h thng s d dng hn l bo v v s h thng con nm ri rc can.Cu hi v bi tp: 1. Trnh by cc phng php nh gi cht lng h thng ATTT. 2. Phn tch nhng nguyn nhn a n thng tin trn a b mt ? Nu cc bin php khc phc. 3. Phn tch nhng nguyn nhn a n r r thng tin trn my tnh? Trnh by cc bin php khcphc.10 11. BI 2 Tn bi : LU TR H THNG THNG TIN TRN CC THIT B LU TRM bi : ITPRG03-19.2Gii thiu : Lu tr d liu an ton v khoa hc l vic rt quan trng trong lnh vc cngngh thng tin. Bi hc cung cp cc kin thc c s v hnh thc, cch thc v thit b lutr, phc hi bo v h thng d liu.Mc tiu thc hin:-S dng c cc thit b lu tr thng dng-Sao lu d liu di nhiu hnh thc.-Phc hi d liu trong mt s trng hp-S dng c mt s phn mm tin ch v phn mm cng c phc hi, bo v cho h thng thng tin.Ni dung chnh: I.Cu trc ca th mc v tp tin trn my n v trn h thng mng my tnh.1. T chc aT chc a l mt trong nhng c trng c bn ca h iu hnh. a mi muahoc a s dng vi mt iu hnh khc khng tng thch vi h iu hnh ang sdng th khng th dng c. Lc ny ta phi tin hnh t chc a cho c cu trc m hiu hnh hin ang dng hiu c.T chc a cho php qun l c cc d liu c ghi trn a nh cc tp tin,qun l vng nh, c/ghi thng tin,...Vic t chc a thng c tin hnh bng chng trnh nh dng a: FORMAT.Khi gi chng trnh ny bng lnh FORMAT chng trnh s t ng thi hnh cc bccn thit t chc a (nh dng a).Chng trnh ny t chc a nh sau : - To ra cc rnh (track) trn b mt a, chia s sector trn 1 rnh, nh s Byte trnmi sector.-Sao chp to tp tin mi (boot record)-To bng cp pht a cho tp tin: bng FAT-To th mc gc (root directory)-Xc nh vng ghi tn, vng lu tr d liu. a trc khi s dng phi c nh dng (format) mi c th lu tr d liu lnc. Mi h iu hnh c cch t chc a ring. HH Windows 98 t chc cu trc atheo dng FAT (file allocation table). Khi nh dng a, HH s chia mi mt a ra thnh nhng ng trn ng tm(track) c nh s t ngoi vo trong v bt u t 0. 11 12. Mi track c chia thnh nhiu on nh gi l cung t (sector), cc cung t c nh s bt u t 1. Mi cung t thng cha 512 bytes. D liu s c lu trn tng cung t. Sector TrackHnh 1 .2: cch phn chia mi mt a khi c nh dng.2. Th mc v tp tin2.1 Tp tin: a) Tp tin (file) :Tp tin l hnh thc, n v lu tr thng tin trn a ca h iu hnh. Ni dung ca tp tin l thng tin cn lu tr. Tp tin (vit tt cho tp thng tin; cn c gi l tp, tp tin, file) l mt tp hp ca thng tin c t tn. Thng thng th cc tp tin ny cha trong cc thit b lu tr nh a cng, a mm, CD, DVD cng nh l cc loi chip in t dng k thut flash c th thy trong cc nh c giao din USB. Ni cch khc, tp tin l mt dy cc bit c tn v c cha trong cc thit b lu tr d liu k thut s. b) c im Mt tp tin lun lun kt thc bng 1 k t c bit (hay du kt thc) c mASCII l 255 h thp phn. K t ny thng c k hiu l EOF ( End OfFile). Mt tp tin c th khng cha mt thng tin no ngoi tr tn v du kt thc.Tuy nhin, iu ny khng h mu thun vi nh ngha v bn thn tn ca tptin cng cha thng tin. Nhng tp tin ny gi l tp tin rng hay tp tintrng. di (kch thc) ca tp tin c th ch ph thuc vo kh nng ca my tnh,kh nng ca h iu hnh cng nh vo phn mm ng dng dng n. n vnh nht dng o di ca tp tin l byte. di ca tp tin khng bao gm di ca tn tp tin v du kt thc. c) Thuc tnh Nhng c tnh v gii hn ca tp tin gi l thuc tnh ca tp tin. Cc loi thuc tnh Ty theo h thng tp tin m cc thuc tnh ny c th khc nhau. Th d cc thuc tnh trn h thng tp tin FAT bao gm: Archive: lu tr. Trn cc h iu hnh DOS th thuc tnh ny c nh khi mi khi tp tin b thay i, v b xa khi thc hin lnh backup sao lu d liu. Hidden: n. Khi mt tp tin c thuc tnh ny th cc chng trnh lit k cc tp tin theo mc nh s b qua, khng lit k tp tin ny. Ngi s dng vn c th lm vic trn tp tin ny nh bnh thng. Read-only: ch c. Khi mt tp tin c thuc tnh ny th cc chng trnh x l tp tin theo mc nh s khng cho php xa, di chuyn tp tin hoc thay i ni dung 12 13. tp tin. Cn cc thao tc khc nh i tn tp tin, c ni dung tp tin vn c cho php. System: thuc v h thng. Mt tp tin c thuc tnh ny s chu cc hn ch bao gm cc hn ch ca thuc tnh Hidden v cc hn ch ca thuc tnh Read-only, ngha l khng b lit k, khng th xa, di chuyn, thay i ni dung. Thuc tnh ny ch yu dng cho cc tp tin quan trng ca h iu hnh. Sub-directory (hay directory): th mc con. Nhng tp tin c thuc tnh ny c x l nh l th mc. Th mc l tp tin dng c bit, ni dung khng cha d liu thng thng m cha cc tp tin v cc th mc khc. Ngoi ra, cn rt nhiu thuc tnh khc ca cc tp tin m ty theo h iu hnh s cnhnghathm vo. Th d i vi h iu hnh Linux cc tp tin c th c thm cc thuc tnh nh cc quyn s dng tp tin, c im ca tp tin, v thng tin v cc loi tp tin nh l cc loi tp tin lin kt mm, cc socket, cc pipe ... Lu : Cc thuc tnh ca mt tp tin thng khng nh hng n ni dung thng tin ca tp tin nhng li nh hng rt nhiu n chc nng v vic x dng tp tin. Th d cc tp tin khng c thuc tnh cho php thi hnh th khng th xem l mt phn mm kh thi c mc d ni dung ca n c th ch cha cc ch th my tnh. Cch lm tp tin tr nn kh thi l thay i thuc tnh kh thi ca n hay l phi thay i phn ui ca tn tp tin (nh l trng hp ca h iu hnh Windows - DOS)d) nh dngCu trc ca mt tp tin nh ngha cch thc m tp tin c cha, c thc thi, vth hin trn cc thit b (nh mn hnh hay my in) gi l nh dng ca tp tin. nh dngny c th n gin hay phc tp.nh dng ca tp tin ph thuc vo nhiu yu t trong quan trng nht bao gm: H iu hnh khc nhau v kin trc my tnh khc nhau c th i hi cc nhdng cho tp tin mt cch khc nhau.Th d: Trn cng mt kin trc Intel, tp tin vn bn dng n gin nht to nnbi h iu hnh Linux cng c s khc nhau vi tp tin vn bn ca Windows(hay DOS). D nhin, cc tp tin vn bn ny li cng khng th c c trncc my dng h iu hnh Mac OS (chng khc nhau hon ton v mt kintrc my tnh) nu khng c cc tin ch c bit chuyn i nh dng. Tp tin dng cho cc mc tiu khc nhau cng s c cc nh dng khc nhau.Ngoi s rng buc v nh dng ca h iu hnh, cc tp tin dng trong ccng dng hay cc phn mm khc nhau cng s khc nhau v s khc nhau nyty thuc vo kin trc ca cc ng dng x dng cc tp tin .Th d d hiu nht l nh dng ca mt tp tin vn bn phi khc vi nh dngca mt tp tin hnh nh hay tp tin m thanh. Cc tp tin dng cho cng mt mc tiu cng c th c nh dng khc nhau tutheo nh sn xut no thit k ra n.Th d: Trong cc tp tin hnh v ha th cc tp tin kiu Bitmap (cc tp hnhc ui l .bmp) c nh dng hon ton khc vi cc tp tin kiu Tagged ImageFile Format (ui ca lai tp tin ny l .tif) v cng khc vi tp tin kiu JointPhotographic Experts Group (vi cc ui c dng .jpg hay .jpeg).e) Tn Ty theo h iu hnh m c th c cc qui c v tn tp tin. di ca tn tp tin ty thuc vo h thng tp tin. Ty thuc vo h thng tp tin v h iu hnh m s c mt s k t khngc dng cho tn tp tin. Th d: Trn h iu hnh Microsoft Windows, khng c dng cc k t sau trongtn tp tin:/ : * ? " < > | Theo truyn thng c ca h thng DOS v Windows, tn tp tin thng bao gm haiphn: phn tn v phn m rng (cn gi l phn ui). Tuy nhin, tn ca mttp tin khng nht thit phi c phn m rng ny.13 14. Th d v cu trc bit ca tp tin ASCIIHnh 1.3 : cu trc bit ca tp tin ASCII Trong hnh trn l hai tp tin vn bn dng n gin dng m ASCII. Tp tin "hoso.txt" l tp tin son ra bng lnh edit ca h iu hnh Windows. Tp tin th nh, "hoso2.txt", li c son tho bng lnh vi trong h iu hnh Linux. Hy lu qui c xung hng ca tp tin trong Windows s bao gm hai byte: du CR (cariage return) c gi tr ASCII l 0x0D v du LF (line feed) c gi tr 0x0A; trong khi , Linux ch cn du LF l . iu ny cho thy s khc nhau v nh dng.2.2 Th mcTh mc (Directory, FOLDER) :Khi s lng tp tin trn a nhiu n hng trm, hng ngn tp tin th vic tm li mt haymt nhm cc tp tin no s kh khn. d dng tm kim, cn to cc th mc cha cc tp tin cng ch , chc nng vo trong mt th mc.Th mc l hnh thc, n v qun l tp tin ca h iu hnh. Ni dung ca th mc l cctp tin m n qun l.Cc th mc trn a c t chc theo dng phn cp, cc th mc xut pht t mt thmc chnh trn a gi l th mc gc (root directory). V cch t chc th mc trn aging nh mt ci cy nn s th mc trn a gi l cy th mc (directory tree).Th mc gc c k hiudo chng trnh nh dng a to ra. Cc th mc c totrong qu trnh lm vic gi l cc th mc con (subdirectory).Trn a khng c sn cy th mc ca n. Khi nh dng a h iu hnh to ra th mcgc. Sau ngi s dng s to ra cc th mc con khi cn. Mt s th mc c ccchng trnh to ra trong lc ci t. Cc tp tin nn c t trong th mc con, ng tngay vo th mc gc.Mt khi s lng tp tin c lu tr trn b nh ngoi ln ti 1 con s kh ln th nhtthit phi a ra khi nim th mc. Khi nim ny cng gn ging nh h thng th mctrong th vin (khi mi tp tin c th v nh 1 cun sch).Nu s sch khng l trong th vin khng c t chc theo mt trt t hp l m c chung vo mt ch th khi mun tm 1 cun sch (theo 1 ch no m ta cha bit tnca cun sch chng hn), ta phi nhn vo tng cun mt, v khng phi th nhn tipqua cun khc cho n khi tm c. Cch lm c th khin ta phi mt 1 khong thigian rt kinh khng, nht l khi cun sch mun tm khng c trong th vin th ta vnphi xem ht tt c mi cun sch trong th vin mi bit c l khng c! khc phctr ngi ngi ta t chc h thng th mc: danh mc tn sch c lit k theo tngch , trong mi ch li c th c nhiu ch con. Vic t chc phn cp dng cynh vy chc chn s gip cho thi gian tm kim 1 cun sch theo 1 ch no dcha bit tn sch cng s rt nhanh.Ni dung cc tp tin cn a dng hn ni dung ca cc quyn sch (khng ch l ti liu vnbn bnh thng m cn c th l hnh nh, m thanh, nhc, phim, tr chi, chng trnhcc loi...), v s lng tp tin trn b nh ngoi cng rt nhiu khin cho vic tm kim &s dng chng cng s rt kh khn nu nh ta cng chung vo 1 ch m khng t chc 14 15. theo mt trt t hp l. Do t chc h thng th mc phn cp trn b nh ngoi l rtcn thit, gii quyt nhu cu trn.Tm li, khi nim th mc cng c a ra bi h iu hnh, vic tm kim & s dngtp tin c hiu qu. Mi th mc c th cha cc tp tin v cc th mc con bn trong (dnhin trong mi th mc cng c th ch cha ton tp tin, hoc ch cha ton th mc con,hoc ang l th mc rng khng cha g c).II.Cch lu tr d liu qua h thng bng FAT (FAT 16, FAT 32, FATNTFS...)T chc h thng tp tin trn a1. Cc nhn xt & phn tch cn thit: c th lu tr c thng tin /d liu vo a & truy xut, s dng c cc dliu trn a mt cch hiu qu th cn phi a ra nhng phn tch, nhn xt sau:i) Phi xc nh cc v tr cn trng ( c th lu d liu vo a) ii) Mi sector(hoc tng qut hn l mi block) ch thuc ti a 1 tp tin, tc nu sector chani dung ca 1 tp tin th trong sector s khng c ni dung ca tp tin khc( d qun l, khng b nhm ln thng tin gia 2 tp tin) iii) Tn & cc thuc tnhca tp tin cn c lu ring vo 1 vng ( tc truyxut d liu nhanh hn) iv) Phi c thng tin v tr bt u ca ni dung tp tin (dophn tch trn) v) Ni dung tp tin khng bt buc phi lin tc (phi cho php c lutr vocc vng khc nhau khi cn phn mnh) vi) Phi bit cc v tr cha ni dungtp tin (do phn tch trn) vii) Phi bit cc v tr b h viii) Ni dung tp tin nn lu trtheo n v l CLUSTER (l dy N sector lin tip d qun l & vic truy xut c nhanh hn)2. Cluster2.1. Khi nimn v c ghi trn a l sector, nhng n v lu tr ni dung tptin khng phi l mt sector m l mt cluster gm N sector lin tipi v tr lu gi ni dung tp tin trong cc phn tch trn s tn ti trn vng d liu (vng DATA) nicha ni dung tp tin.2.2. L do pht sinh khi nim Clusteri)Nu sector trn vng d liu qu nhiu th c th s kh hoc khng qun l c,khi qun l trn cluster s d dng hiu qu hn.ii) Ni dung tp tin thng chim nhiu sector v c th khng lin tc, v thi gian cghi mt ln n sector lin tip thng nhanh hn nhiu so vi thi gian c ghi n lnm mi ln ch 1 sector. Do ti u thi gian truy xut tp tin th cn chn n vtruy xut l mt khi nhiu sector.2.3. Hnh thc t chca s c chia thnh 2 vng: vng d liu (DATA) cha ni dung tp tin v vng hthng (SYSTEM) cha cc thng tin qun l. Vng SYSTEM c kch thc nh hn nhiuso vi vng DATA v phi truy xut mi khi s dng a nn thng nm ngay u a,phn cn li thuc v vng DATA. Trn vng DATA l mt dy cc Cluster lin tip cnh ch s theo th t tng dn (bt u t 0, 1 hay 2 ty theo H iu Hnh). Nh vynu vng DATA c SD sector & bt u ti sector SS, mi Cluster chim SC sector, Clusteru tin c nh ch s l FC, th a s c tng cng SD/Sc Cluster v Cluster C s btu ti sector: SS + (C FC ) * SCV d, nu a c kch thc 4014 sector, vng SYSTEM chim 11 sector, micluster chim 4 sector, Cluster u tin c nh ch s l 2; th phn b Cluster trn as nh sau:Cluster 2Cluster 3 Cluster 4... Cluster 1001 ...... 15 16. 0 1 ... 10 11 12 13 14 15 16 17 18 19 20 21 22 DATA AREA ... 4007 4008 4009SYSTEM AREA4010 Hnh 1.4 : phn b Cluster trn a( 3 sector 4011, 4012, 4013 s khng thuc cluster no v khng c s dng)2.4. Kch thc Cluster S sector trn 1 cluster nn l ly tha ca 2 v c gi tr ln hay nh l ty theo a.Nu ta chn kch thc cluster cng ln th s cng lng ph a v mt tp tin c kch thcnh vn phi dng mt cluster gm nhiu sector lu, nhng khi s hn ch c sphn mnh ca tp tin v v vy tp tin c th an ton hn & truy xut nhanh hn. Kchthc ca Cluster ph thuc vo kh nhiu yu t: dung lng a, tc truy xut 1 dysector trn a, kch thc ca a s tp tin s lu vo a, s cluster ti a m h thng cth qun l, nhu cu ca ngi s dng, Trn cc a cng hin ti th Cluster thng ckch thc 4, 8 hoc 16 sector.V d:-Vi a mm 1.44 MB bnh thng (c 2880 sector), nu ta cho 1 cluster chim 1000sector th s rt khng hp l. V khi ta ch c th chp c ti a 2 tp tin voa, du mi tp ch c kch thc l 1byte! Tuy nhin nu ta ch ton chp vo acc tp tin c kch thc gn 1000 sector th s khng cn s lng ph na.-Vi h thng ch c th qun l ti a M Cluster, nu vng DATA ca a c 100Msector th ta phi cho mi Cluster ti thiu 100 sector mi c th qun l c tonb vng DATA3. Bng qun l Cluster3.1. Khi nimL 1 dy phn t, mi phn t thng l 1 con s nguyn c dng qun l 1cluster trn vng d liu. Vic qun l y c th l cho bit cluster tng ng ang trng thi trng, h, hay ang cha ni dung ca 1 tp tin, v cho php xc nh danh schcc cluster cha ni dung ca tp tin. C th dng 1 bng p ng cc nhu cu trn,nhng cng c th t chc nhiu bng mi bng phc v cho 1 nhu cu.3.2 L do pht sinh a ni dung tp tin vo a th phi xc nh cc cluster cn trng (phn tch (i)), c ni dung tp tin trn a th phi xc nh c danh sch cc cluster cha ni dung tptin (phn tch (vi)), tuy c th lu thng tin qun l ngay trn cluster nhng khi truyxut rt chm nn nht thit phi lp ra bng ny qun l truy xut nhanh hn.3.3. Hnh thc t chc xc nh cc cluster trng, h, hay thuc trng thi lun l c bit no (nhngtrng thi ch mang 1 trong 2 gi tr: C Khng) ta c th qun l theo dng ch mc: miphn t ca bng qun l l 1 con s ni ln trng thi ca cluster mang ch s tng ng. mc n gin ta ch cn qun l 2 trng thi lun l l cluster trng & cluster h. Danhsch cc cluster h c th lu trc tip (c bao nhiu cluster h th danh sch c by nhiuphn t), v s cluster h trn a s rt t. Vic qun l cluster trng c th dng hnh thcbitmap (mi bit qun l 1 cluster tng ng): nu mun bit cluster K l trng hay khng taxem gi tr ca bit K l 0 hay 1. Ta cng c th qun l vng trng bng cch lu 1 danhsch cc phn t, mi phn t cha v tr bt u & kch thc ca vng trng tng ng.Vic xc nh mt trng thi lun l ca cluster c th thit k kh n gin, vn chyu l hnh thc t chc c th xc nh chui cc cluster cha ni dung ca 1 tp tin, cmt s hnh thc c bn nh sau:1. 3.3.1 Lu tr ni dung tp tin trn dy cluster lin tip ...2. 3.3.2 S dng cu trc danh sch lin kt ...3. 3.3.3 S dng cu trc danh sch lin kt kt hp ch mc:16 17. Ta t chc 1 bng cc phn t nguyn (dy s nguyn), mi phn t c dng qun l 1 cluster trn vng d liu theo dng ch mc (phn t K qun l cluster K). Vi quinh:. Nu phn t K trn bng c gi tr l FREE th cluster K trn vng d liu ang trng thi trng.. Nu phn t K trn bng c gi tr l BAD th cluster K trn vng d liu s c hthng hiu l trng thi h.. Nu phn t K trn bng c gi tr khc FREE v khc BAD th cluster K trn vngd liu ang cha ni dung ca 1 tp tin. Khi ny ta cn bit c cluster k tip chani dung ca tp tin: nu phn t K ca ba?ng c gi tr L v L = EOF th cluster K lcluster cui cng ca tp tin, nu L EOF th phn k tip ca ni dung tp tin nm ticluster L (qun l theo dng danh sch lin kt).Nh vy hnh thc t chc ny c th p ng c tt c cc nhu cu qun lcluster: xc nh cluster trng, h, hay ang cha ni dung tp tin, v chui cc cluster chani dung ca mt tp tin (khi bit cluster bt u).V d, nu ni dung bng qun l Cluster ca a trn nh sau: Hnh 2.4: Bng qun l Cluster trn a0 1 2 3 4 5 6 7 8 9 10 11 12 13 ... 1001(cc phn t t 13 n 1001 u c gi tr l FREE)th t y c th xc nh lc ny trn a ang c 2 cluster h, 990 cluster trng, 8 clusterchani dung tp tin. C th l: -Cc cluster h: 4, 10 -Cc cluster trng: 8, 13, 14, 15, , 1001-Cc cluster cha ni dung tp tin: 2, 3, 5, 6, 7, 9, 11, 12. Trong c 3 tp tin: + tp tin I chim 3 cluster theo ng th t l: 2, 3, 5. + tp tin II chim 1 cluster duy nht l: 6. + tp tin III chim 4 cluster theo ng th t l: 9, 7, 11, 12.Lu : Phn t u tin ca bng c ch s l 0 nn nu Cluster u tin ca vng DATAc nh ch s l FC > 0 th FC phn t u tin ca bng (t 0 .. FC -1) s khng cdng qun l Cluster, m bo tnh cht ch mc (phn t mang ch s K qun l trngthi ca Cluster mang ch s K). Khi ny khng gian b lng ph hon ton khng ng k,nhng vic qun l truy xut th tin li hn, ta cng c th tn dng phn khng gian tngng vi FC phn t u bng ny lu 1 thng tin qun l no .Gi tr ca cc phn t trn bng:Ta cn phi t ra 3 gi tr hng c bit l FREE, BAD v EOF tng ng vi 3 trngthi cluster: trng, h, hoc l cluster cui ca ni dung tp tin, ta cng c th t thm 1 sgi tr c bit na cho nhng trng thi c bit khc ca cluster (nu c) hoc 1 s gi trdnh ring phc v cho nhng nhu cu trong tng lai. Nhng gi tr cn li s tngng vi trng thi cluster ang cha ni dung tp tin v lc gi tr ca phn t cng chnhl ch s ca cluster k tip.Cc hng c bit (v dnh ring nu c) phi khc vi cc gi tr c th c trn ch scluster th cluster tng ng mi c th s dng c. V d, vi hnh trn, nu ta t hngEOF = 7 th tp tin III s b hiu lm l ch chim ng mi cluster 9 ch khng phi chim 4cluster!Mi phn t trn bng nn l 1 con s nguyn dng c th qun l c nhiucluster hn, khi ny cc hng c bit nu trn s khng th l s m m phi chim nhnggi tr ln nht c th biu din c, v ch s ca cluster cui cng trn vng DATA buc17 18. phi nh hn nhng gi tr hng c bit ny. Trong trng hp cluster u tin c nhch s l FC v FC > 0 th cng c th s dng cc gi tr 0..FC-1 cho nhng hng c bittrn.3.4. Kch thc ca bng qun l ClusterMi phn t trn bng l 1 con s nguyn nn pht sinh vn phi lu tr mi snguyn bng bao nhiu bit. Ta c th cn c vo ch s cluster cui cng trn vng DATA xc nh gi tr ti a cn biu din c ca mi phn t v gi tr ca cc hng c bit suy ra s bit ti thiu ca mi phn t, n gin c th dng 16bit hoc 32bit cho miphn t ty theo a c kch thc nh hay ln. Vn phc tp nm ch lm sao xcnh s phn t ca bng, cng nh s cluster trn vng DATA. V khi to (nh dng) a thta ch c kch thc ca a, ch khng c kch thc vng DATA, v khng th t t rakch thc cho n nh vi nhng thnh phn khc. Ta c th gii quyt bng cch gi nhkch thc ca bng l 1 sector & kim chng li xem c hp l hay khng, nu khng thtng dn kch thc ca bng cho n khi hp l.3.5. T chc qun l cluster trn h iu hnh DOS & Windows 9xBng qun l cluster trn DOS & Windows 9x c gi l FAT (File Allocation Table),c t chc theo hnh thc danh sch lin kt kt hp ch mc. Trn DOS mi phn t cabng FAT c biu din bng 1 con s nguyn 12bit hoc 16bit (bng FAT tng ng ctn l FAT12 hoc FAT16). Trn Windows cng c 2 loi FAT trn v c thm loi FAT32(mi phn t c lu bng 32bit).Nu phn t K ca FAT c gi tr L th trng thi ca Cluster K l:Gi tr ca L Trng thi ca Cluster K FAT12 FAT16FAT32 Trng000 H FF7FFF7 FFFFF7 Cluster cui ca tp tin FFFFFFF FFFFFF Cha ni dung tp tin v c cluster k sau l L 2 .. FEF 2 .. FFEF2..FFFFEF Hnh 1.5 : Trng thi ca Cluster KC mt s gi tr tuy vn thuc phm vi biu din nhng khng th c vi L (v d, viFAT12 l cc gi tr 1, FF0 .. FF6, FF8 .. FFE), y l cc gi tr dnh ring c d phng c th s dng cho nhng trng thi c bit khc ca cluster trong nhng phin bn sauca h iu hnh, khi s vn c c s tng thch gia cc phin bn c & mi.Chnh v gi tr 0 c dng biu din trng thi cluster trng nn s khng th tn ticluster mang ch s 0 trn vng d liu, DOS & Windows nh ch s ca cluster u tintrn vng d liu l 2 (FC = 2)Cng t nhng gi tr tng ng vi trng thi cluster cha ni dung tp tin bng trn,ta c th suy ra s cluster ti a m bng FAT12 c th qun l c l FEE (tc 4078d,12ch khng phi l 2 = 4096), v FAT16 l FFEE (tc 65518d). Nh vy nu s cluster trnDATA khng qu 4078 th h thng s dng FAT12 qun l, nu s cluster ln hn 4078nhng khng qu 65518 th s dng FAT16, v ln hn 65518 th s dng FAT32. Tuynhin l qui c mc nh ca h iu hnh, ta cng c th ch nh loi FAT cn sdng, v d vng DATA c 2004 cluster th dng FAT16 qun l vn c. Bng qun l cluster rt quan trng nn DOS & Windows thng lu thm N bngbackup phng trnh h hng (N0, thng l 1). Cc bng FAT c lu tr k tipnhau trn 1 vng gi l vng FAT. 18 19. Vi bng FAT12, vic truy xut mt phn t hi phc tp: n v truy xut trn RAM l 1byte nhng mi phn t li c kch thc 1.5 byte. Ta c th xc nh 2 byte tng ngcha gi tr ca phn t, ly gi tr s nguyn khng du 2byte ti ri dng cc php tonx l trn bit truy xut c con s 1.5 byte tng ng.V d, ni dung 12 byte u ca bng FAT l:F0 FF FF 03 40 00FF 7F FF AB CD EFoffset 0 1 2 3 4 5 6 7 8 9 A Bth 8 phn t u tng ng ca bng FAT l:FF0 FFF 003 004 FFF FF7DAB EFCphnt 0 1 2 3 4 5 6 7V kch thc bng FAT12 l kh nh (ti a 12 sector) nn vic truy xut 1 phn tc n gin ngi ta thng c ton b cc sector trn bng FAT vo 1 vng m ri tvng m ny xy ng ra 1 mng s nguyn 2byte m mi phn t ca mng mang gi trca phn t tng ng trn bng FAT. Khi cn lu bng FAT vo a th li thc hin thaotc ngc li: t mng s nguyn 2 byte to ra dy byte tng ng ca FAT a vo vngm v lu vng m vo cc sector cha FAT trn a.4. Bng th mc4.1 Khi nim v RDET (Root Directory Entry Table):L 1 dy phn t (entry), mi phn t cha tn & cc thuc tnh ca 1 tp tin trn thmc gc ca a (hoc l phn t trng cha thuc v 1 tp tin no ht).V d, nu m hnh thuc tnh tp tin c thit k ch gm cc thnh phn: tn chnh(chui ti a 4 k t), tn m rng (chui ti a 2 k t), kch thc tp tin (s nguyn 2byte) th RDET s nh sau:OffsetHnh 1.6 : RDET4.2 L do pht sinh khi nim RDETT phn tch (iii).4.3 Kch thc RDETS entry trn RDET c qui nh bi chng trnh nh dng (format) a, con sny s ln hay nh l ty theo dung lng ca a (nhng chc chn l s khng qu ln vs tp tin trn a d rt nhiu th s tp tin th mc gc cng khng nn qu nhiu, sgy kh khn cho vic qun l ca ngi s dng). S entry trn RDET khng bt buc phil 1 gi tr chnh xc m cho php dao ng mt t, v vy ta c th iu chnh hn chlng ph khng gian lu tr trn sector. V d, nu mi entry c kch thc 32 byte & ta dnh t chc 50 entry cho RDET th khng hay lm, c th iu chnh li thnh 48 entry hoc64 entry. 19 20. 4.4 Cu trc Entry ca DOSArchiveDirectoryaLabelSystemHidden ReadOnly + ReadOnly: thuc tnh ch c, khi tp tin c thuc tnh ny h thng s khng cho php sa hoc xa. + Hidden: thuc tnh n, trng thi mc nh h thng s khng hin th tn ca cc tp tin ny khi lit k danh sch tp tin. + System: thuc tnh h thng, cho bit tp tin c phi thuc h iu hnh khng + a Label: thuc tnh nhn a, trn RDET ch c ti a 1 entry c thuc tnh ny, khi entry khng phi tng ng vi tp tin m c dng cha nhn ca a l 1 chui ti a 11 k t c lu 11 byte u tin ca entry + Directory: thuc tnh th mc, nu entry c thuc tnh ny th tp tin tng ng khng phi l mt tp tin bnh thng m l mt tp tin th mc. Mi th mc trn DOS c lu tr ging nh mt tp tin bnh thng, ni dung ca tp tin th mc ny l danh mc nhng tp tin v th mc con ca n. + Archive: thuc tnh lu tr, cho bit tp tin c backup hay cha (bng lnh backup ca h iu hnh), y l thuc tnh hu nh khng c s dng v t khi c nhu cu backup tt c cc tp tin m ch cn lu nhng tp tin cn thit. Khi ta xa tp tin, entry tng ng phi c chuyn sang trng thi trng, nhng20 21. trng thi trng lc ny khng phi l 32 byte ca entry c chuyn sang gi tr 0 m ch cbyte u tin c i thnh E5. V tt c cc k t ca tn tp tin u khng th c m l 0hoc E5 nn bit 1 entry c trng hay khng ta ch cn nhn gi tr byte u tin ca entry:nu khc 0 v E5 th khng phi l entry trng. Mi khi tm entry trng s dng hthng tm theo th t t u tr i nn nu ta gp 1 entry trng c byte u l 0 th tt ccc entry pha sau cng l nhng entry trng dng cha tng uc s dng (32 byte trnentry u l 0)4.5 Bng th mc con SDET (Sub Directory Entry Table):4.5.1 Khi nim: Mi th mc trn DOS c lu tr ging nh mt tp tin bnh thng. Ni dung catp tin th mc ny l mt dy entry, mi entry cha tn & thuc tnh ca nhng tp tin vth mc con thuc th mc ang xt ging y nh cc entry trn RDET, dy entry ny cgi l SDET. C th ni mt cch n gin rng SDET l ni dung ca tp tin th mc.SDET c cu trc t chc ging nh RDET nhng c lu tr ngay trn vng DATA (v lni dung tp tin). Trn a c ng 1 RDET nhng c th c rt nhiu SDET v cng cth khng c bng SDET no.4.5.2 L do pht sinh Nu s tp tin trn a c th nhiu th nht thit phi a ra khi nim th mc trnh chuyn tt c mi tp tin trn a phi lu chung vo 1 ni rt kh qun l. V ccthuc tnh ca th mc kh ging vi cc thuc tnh ca tp tin bnh thng nn c th tra khi nim th mc l mt tp tin c bit v t chc lu tr nh mt tp tin bnh thng,khng cn phi a ra mt thit k khc cho vic t chc lu tr h thng th mc.4.5.3 Kch thc SDET S entry trn SDET c th rt nh m cng c th rt ln, ph thuc vo s lngtp tin & th mc con bn trong th mc ang xt ch khng b qui nh 1 con s c nhnh trn RDET. V SDET nm trn vng DATA nn ti u s entry ca SDET thngc t sao cho khng b lng ph khng gian trn cluster. V d, nu entry c kch thc32 byte v cluster c c kch thc 32 sector th s entry ca SDET s l bi ca 512.4.5.4 Bng SDET trn DOS Lun c 2 entry . v .. u bng m t v chnh th mc ny v th mc cha can. Cu trc mi entry trn SDET cng ging nh entry trn RDET, ch khc s lngentry & v tr lu gi ni dung entry trn SDET l khng c nh. V SDET lun chim trncluster nn thuc tnh kch thc tp tin trn entry tng ng vi th mc s khng cn sdng v lun c DOS gn l 0. Nh vy khi to 1 th mc th s entrytrong SDET ca th mc s l SC/32 (SC l kch thc cluster), trong entry u tin cphn tn l . v phn cn li lu cc thng tin v th mc ny, entry th hai c phn tn l.. (2 byte u ca entry lu k t . v 9 byte k sau lu khong trng) v phn cn li lucc thng tin v th mc cha ca th mc ny, t entry th ba tr i u l entry trng(32byte u mang gi tr 0). Nu chp vo trong th mc con ny nhiu hn (SC/32 -2) tptin th bng SDET hin ti khng s entry qun l, khi ny kch thc bng SDET sc h thng cho tng thm bng cch tm cluster trng trn vng DATA v lu ni dungcc entry pht sinh thm vo cluster mi ny (v phn cn li ca cluster nu c cng clu cc entry trng nh trn cluster u tin).1. 5. Boot Sector2. 5.1 Khi nimL sector u tin ca a, cha mt on chng trnh nh np h iu hnhkhi khi ng my v cc thng s quan trng ca a: kch thc cluster, kch thc bngth mc, kch thc bng qun l cluster, ...5.2 L do pht sinh Cc bng qun l cluster & bng th mc p ng cc phn tch nu trn,nhng tht s c th thc hin c cc thao tc truy xut a ta cn phi bit c v tr& kch thc ca tng thnh phn trn a. V a c th c kt ni vo mt h thngkhc nn thng tin v cc thnh phn ca a phi c lu ngay trn chnh a bt21 22. c h thng no cng c th hiu. Sector u tin ca a l ni thch hp nht cha ccthng tin quan trng ny.5.3 Hnh thc t chcCc thng s quan trng ch chim 1 kch thc nh nn ta c th qui c mt vngnh trn sector dng cha cc thng s ca a (phn cn li l on chng trnh nph iu hnh khi khi ng), mi thng s c qui nh nm ti mt offset c th c nhno . Trong trng hp tng kch thc cc thng s v phn chng trnh np h iuhnh ln hn 512byte th c th dng tip nhng sector k sau lu5.4 T chc thng tin trong BootSector ca DOS & Windows5.4.1 Boot Sector ca h iu hnh DOSOffsetS byte ngha0 (0h)3 Lnh nhy n u on m Boot (qua khi vng thng s)3 (3h)8 Tn cng ty /version ca HH11 (0Bh)2 S byte ca sector13 (0Dh)1 S sector ca cluster14 (0Eh)2 S sector trc bng FAT16 (10h)1 S lng bng FAT17 (11h)2 S Entry ca RDET19 (13h)2 S sector ca a21 (15h)1 K hiu loi a22 (16h)2 S sector ca FAT24 (18h)2 S sector 1 track (tnh theo sector)26 (1Ah)2 S lng u c (head)28 (1Ch)4 Khong cch t ni m t a n u a32 (20h)4 Kch thc a (nu s 2 byte ti offset 13h l 0)36 (24h)1 K hiu vt l ca a cha a (0 : mm, 80h: cng)37 (25h)1 Dnh ring38 (26h)1 K hiu nhn din HH39 (27h)4 SerialNumber ca a43 (2Bh)11a Label54 (36h)8 Dnh ring62 (3Eh)448 on chng trnh Boot np tip HH khi khi ng my510 (1FDh)2 Du hiu kt thc BootSector /Master Boot (lun l AA55h) Hnh 1.7 : Boot Sector ca h iu hnh DOSV d, vi a c na u ca Boot Sector nh sau:EB 3C 90 4D 53 57 49 4E-34 2E 31 00 02 10 01 00 . 1 th lu tip vo cc v tr SB + SF , SB + 2*SF ,..., SB +(nF-1)*SF ) -Bc 5: To 1 vng m kch thc SR (byte) c ni dung cc byte u l 0. -Bc 6: Lu li vng m trn vo bng RDET trn a (lu vo SR sector bt uti sector (SB + nF*SF ) )3. c ni dung tp tin trn a3.1 Khi nimy l thao tc truy xut a c thc hin nhiu nht, cng l thao tc thng27 28. xuyn ca h thng my tnh. M tc truy xut b nh ngoi (ni cha tp tin) chm hnnhiu so vi b nh trong, do tng tc hot ng ca my tnh ng thi cth bo mt d liu, kim chng s hp l, khng vi cc s c c th gy h hng, ... khi truy xut tp tin ngi ta thng dng ti nhiu h thng Cache, nhiu k thut ti u &cc x l khc. Tuy nhin c th d dng hn cho vic nm c mt cch c bn tchc lu tr tp tin & c ch hot ng ca h thng qun l tp tin, cc thut gii ctrnh by sau y ch nu cch gii quyt c bn, chn phng nht - khng quan tm nhiun vic ti u & cc x l nng cao khc.Ta bit v c bn c 2 loi tp tin khc nhau: tp tin bnh thng v tp tin thmc (cn gi l th mc con). Cho nn trc mt c th thy c 2 thao tc khc nhau: cni dung tp tin bnh thng & c ni dung bng th mc con (tc ni dung tp tin thmc). Nhng tht ra 1 tp tin bnh thng cng nh 1 th mc cng c th nm trong 1 thmc con no , v vy c th phn ra ti 4 thao tc tng i ring bit: c ni dung 1 tptin bnh thng th mc gc ca a, c ni dung 1 th mc con nm th mc gc caa, c ni dung 1 tp tin bnh thng 1 th mc con ca a, v c ni dung 1 th mccon nm trong 1 th mc con no ca a.3.2 c ni dung tp tin th mc gc ca a3.2.1 Thut gii:(u vo: tn a, tn tp tin cn ly ni dung; u ra: ni dung ca tp tin) Bc 1: c BootSector ca a xc nh cc thng s cn thit (v tr & kch thc ca bng th mc gc & bng qun l cluster, kch thc cluster, v tr bt u ca vng d liu,...) Bc 2: c bng th mc gc vo b nh. Bc 3: Tm trn bng th mc gc va c entry c phn tn ging vi tn tp tin cn ly ni dung (nu khng c th thng bo tp tin khng tn ti & thot). Bc 4: c bng qun l cluster vo b nh. Bc 5: T ni dung bng qun l cluster va c & thng tin ca entry tm c bc 3 suy ra danh sch nhng cluster cha ni dung tp tin. Bc 6: c nhng cluster tng ng vi danh sch trn & ghp cc ni dung c c li theo ng th t ta c ni dung tp tin (ring phn ni dung trn cluster cui ch ly N byte, vi N = MOD ).3.2.2 c ni dung tp tin th mc gc ca a c kin trc FAT12 /FAT16 -Bc 1: c BootSector xc nh cc thng s SB, SF, SR, SC, SS. -Bc 2: c bng RDET vo b nh. -Bc 3: Tm trn bng RDET va c entry c phn tn ging vi tn tp tin cn ly ni dung (nu khng c th thng bo tp tin khng tn ti & thot). -Bc 4: c bng FAT vo mng aFAT trn b nh. -Bc 5: T ch s cluster bt u f1 trong entry tm c bc 3 xc nh dy cc phn t k tip f2, f3, f4 , ... theo cng thc fi+1= aFAT [ fi ] cho n khi gp ch s fN c aFAT[ fN ] = EOF. -Bc 6: c nhng cluster f1, f2, f3 , ..., fN & ghp cc ni dung c c li theo ng th t ta c ni dung tp tin (ring phn ni dung trn cluster fN ch ly M byte, vi M = MOD SC ).3.3 c ni dung mt th mc con th mc gc ca a Vic s dng ni dung tp tin bnh thng v ni dung ca tp tin th mc l honton khc nhau. Nhng nu t chc lu tr tp tin th mc ging nh tp tin bnh thng thvic c ni dung bng th mc con cng s ging nh c ni dung tp tin bnh thng.Ring i vi a c t chc theo cu trc FAT12 /FAT16 th phn ni dung tp tin thmc trn cluster cui cng c s dng ht ch khng nh tp tin bnh thng c th ch28 29. chim 1 phn. V cng v vy trng trong entry ca tp tin th mc skhng c s dng (lun c gn l 0), d bng th mc c kch thc bao nhiu i na.3.4 c ni dung tp tin trong mt th mc con ca aEntry cha cc thng tin v tp tin cn c s nm trong bng th mc con ca thmc cha tp tin . C th thy mt vn trc tin l th mc con cha tp tin c thang nm trong 1 th mc con khc, v th mc con ny li c th nm trong 1 th mc conkhc na. Nh vy c c ni dung tp tin trc tin ta phi xc nh ng dn nni cha tp tin (l mt dy cc th mc con m th mc trc l cha ca th mc sau), tng dn ny ta s ln lt c & phn tch cc bng th mc con cui cng c cbng th mc con ca th mc cha tp tin. Gi s cc th mc con trong ng dn cgi theo th t l th mc con cp 1, th mc con cp 2, ... th hnh thc xc nh nidung ca bng th mc con cp N l: -Tm entry tng ng vi th mc con cp 1 trong bng th mc gc v suy cni dung ca tp tin ny (bng th mc con cp 1). -Tm entry tng ng vi th mc con cp 2 trong bng th mc con cp 1 trn vsuy c ni dung ca tp tin th mc con cp 2 (bng th mc con cp 2).o -Tm entry tng ng vi th mc con cp 3 trong bng th mc con cp 2trn v suy c ni dung ca tp tin th mc con cp 3 (bng th mc concp 3) -Tm entry tng ng vi th mc con cp N trong bng th mc con cp (N-1) trnv suy c ni dung ca tp tin th mc con cp N (bng th mc con cp N)3.4.1 Thut gii:(u vo: tn a, ng dn & tn tp tin cn ly ni dung; u ra: ni dung tp tin ) Bc 0: Phn tch ng dn xc nh s cp (gi s l N) & tn ca cc thmc con cc cp. Bc 1: c BootSector ca a xc nh cc thng s cn thit (v tr & kchthc ca bng th mc gc & bng qun l cluster, kch thc cluster, v tr bt uca vng d liu,...) Bc 2: c bng th mc gc vo b nh. Bc 3: c bng qun l cluster vo b nh. Bc 4: Bt u t bng th mc gc ln lt suy ra cc bng th mc con cccp k tip & cui cng c bng th mc con cha entry ca tp tin (th mc con cpN) Bc 5: Tm trn bng th mc hin ti entry c phn tn ging vi tn tp tin cnly ni dung (nu khng c th thng bo tp tin khng tn ti & thot). Bc 6: T ni dung bng qun l cluster c bc 3 & thng tin ca entry tmc bc trn suy ra danh sch nhng cluster cha ni dung ca tp tin. Bc 7: c nhng cluster tng ng vi danh sch trn & ghp cc ni dung cc li theo ng th t ta c ni dung tp tin (ring phn ni dung trn clustercui ch ly N byte, vi N = MOD ). Thut gii chi tit cho Bc 4: Bc 4.1: K = 1. Bc 4.2: Tm trn bng th mc hin ti entry c phn tn ging vi tn th mc con cp K (nu khng c th thng bo ng dn sai & thot). Bc 4.3: T ni dung bng qun l cluster c bc 3 & thng tin ca entry tm c bc trn suy ra danh sch nhng cluster cha ni dung tp tin th mc con cp K. Bc 4.4: c nhng cluster tng ng vi danh sch trn & ghp cc ni dung c c li theo ng th t ta c ni dung bng th mc con ca th mc cp K.29 30. Bc 4.5: Gn bng th mc hin ti l bng th mc con trn Bc 4.6: Nu K < N th tng K thm 1 v quay li bc 4.2.3.4.2 c ni dung tp tin th mc con ca a c kin trc FAT12 /FAT16 -Bc 0: Phn tch ng dn xc nh s cp N & tn cc th mc con cc cp. -Bc 1: c BootSector xc nh cc thng s SB, SF, SR, SC, SS. -Bc 2: c bng RDET vo b nh. -Bc 3: c bng FAT vo mng aFAT trn b nh. -Bc 4: Bt u t RDET ln lt suy ra cc SDET cc cp k tip cho n khi c SDET ca th mc con cp N -Bc 5: Tm trn bng SDET trn entry c phn tn ging vi tn tp tin cn ly ni dung (nu khng c th thng bo tp tin khng tn ti & thot). -Bc 6: T ch s cluster bt u f1 trong entry tm c bc trn xc nh dy cc phn t k tip f2, f3, f4 , ... theo cng thc fi+1= aFAT [ fi ] cho n khi gp ch s fN c aFAT[ fN ] = EOF. -Bc 7: c nhng cluster f1, f2, f3 , ..., fN & ghp cc ni dung c c li theo ng th t ta c ni dung tp tin (ring phn ni dung trn cluster fN ch ly M byte, vi M = MOD SC ).Ghi ch: Ta cng c th kt hp cc bc 5,6,7 vo bc 4.3.5 c ni dung th mc trong mt th mc con ca a Bi ton ny c gii quyt chc nng k trc (bng cch thc hin t ucho n ht bc 4).4. Lu gi tp tin vo a4.1 Khi nimSau thao tc u tin l nh dng a, chc nng k tip c nh hng n nidung lu tr trn a l a tp tin vo a, chc nng ny s c thc hin nhiu lntrong qu trnh s dng a. Vic a 1 tp tin vo a c th l chp 1 tp tin t ni khcvo a, to 1 tp tin trn a, hoc to 1 th mc con trn a. Khi a ang trng thitrng th cc thao tc ch c th thc hin trn th mc gc ca a, nhng khi a cth mc con th nhng thao tc trn c th thc hin trong 1 th mc con no ca a.Ta c th phn ra 4 thao tc tng i ring bit: a 1 tp tin bnh thng vo th mc gcca a, to 1 th mc con th mc gc ca a, a 1 tp tin bnh thng vo 1 th mccon no ca a, to 1 th mc con trong 1 th mc con no ca a.4.2 a 1 tp tin bnh thng vo th mc gc ca a4.2.1 Thut gii:(u vo: tn a, tn & cc thuc tnh ca tp tin, ni dung tp tin; u ra: tn, cc thuctnh & ni dung tp tin c lu vo a theo ng cu trc lu tr thit k - khng nhhng n cc ni dung ang c sn trn a) Bc 1: c BootSector ca a xc nh cc thng s cn thit (v tr &kch thc ca bng th mc gc & bng qun l cluster, kch thc cluster, v tr btu ca vng d liu,...) Bc 2: c bng th mc gc vo b nh. Bc 3: Tm trn bng th mc gc va c 1 entry trng (nu khng c ththng bo ht ch lu tr & thot). Bc 4: T kch thc tp tin & kch thc cluster xc nh s cluster N mtp tin phi chim (= /) Bc 5: c bng qun l cluster vo b nh.30 31. Bc 6: Tm trn bng N phn t tng ng vi trng thi cluster trng (nukhng c N phn t th thng bo khng dung lng trng lu ni dung tptin & thot)Bc 7: iu chnh li gi tr N phn t trn thnh trng thi ca cluster chani dung tp tin (theo ng th t )Bc 8: a vo entry th mc tm c bc 3 tn & cc thuc tnh catp tin.Bc 9: Lu li entry va iu chnh vo bng th mc gc ca a.Bc 10: Lu li bng qun l cluster vo a.Bc 11: Phn ni dung tp tin ra thnh nhng phn c kch thc bng kchthc cluster v lu chng vo N cluster tng ng vi N phn t tm c bc6.4.2.2 a mt tp tin vo th mc gc ca a c kin trc FAT12 /FAT16 -Bc 1: c BootSector xc nh cc thng s SB, SF, nF, SR, SC, SS. -Bc 2: c bng RDET vo b nh. -Bc 3: Tm trn bng RDET va c 1 entry trng (nu khng c th thng bo htch lu tr & thot). -Bc 4: Xc nh s cluster N m tp tin s chim ( N=/SC). -Bc 5: c bng FAT vo mng aFAT trn b nh. -Bc 6: Tm trn mng aFAT N phn t f1, f2, ..., fN c gi tr 0 (nu khng c Nphn t th thng bo khng dung lng trng lu ni dung tp tin & thot). -Bc 7: iu chnh li gi tr N phn t trn theo cng thc: aFAT [ fi ] = fi+1, vi i t1 n (n-1), v aFAT [ fN ] = EOF. -Bc 8: a vo entry th mc tm c bc 3 tn & cc thuc tnh ca tp tin(trng cluster bt u c gn gi tr f1) -Bc 9: Lu li entry va iu chnh vo RDET ca a. -Bc 10: Lu li mng aFAT trn vo nF bng FAT trn a. -Bc 11: Phn vng ni dung tp tin ra thnh nhng on c kch thc bng SCv lu chng vo cc cluster tng ng mang ch s f1, f2, ..., fN trn vng DATA.4.3 To 1 th mc con th mc gc ca a4.3.1 Thut gii:(u vo: tn a, tn & cc thuc tnh ca th mc; u ra: mt th mc rng c to ratrn th mc gc ca a theo ng cu trc lu tr thit k - khng nh hng n ccni dung ang c sn trn a)Bc 1: c BootSector ca a xc nh cc thng s cn thitBc 2: c bng th mc gc vo b nh.Bc 3: Tm trn bng th mc gc va c 1 entry trng.Bc 4: c bng qun l cluster vo b nh.Bc 5: Tm trn bng 1 phn t tng ng vi trng thi cluster trng.Bc 6: iu chnh li gi tr phn t trn thnh trng thi ca cluster chani dung tp tin (v l cluster cui)Bc 7: a vo entry th mc tm c bc 3 tn & cc thuc tnh catp tin th mc.Bc 8: Lu li entry va iu chnh vo bng th mc gc ca a.Bc 9: Lu li phn t va iu chnh bc 6 vo bng qun l clusterca a.Bc 10: To 1 vng m c kch thc bng kch thc cluster v a vo 31 32. vng m ni dung ca bng th mc con tng ng vi 1 th mc rng Bc 11: Lu vng m trn vo cluster tng ng vi phn t tm c bc 6.4.3.2 To 1 th mc con trn th mc gc ca a c kin trc FAT12 /FAT16 -Bc 1: c BootSector xc nh cc thng s SB, SF, nF, SR, SC, SS. -Bc 2: c bng RDET vo b nh. -Bc 3: Tm trn bng RDET va c 1 entry trng. -Bc 4: c bng FAT vo b nh. -Bc 5: Tm trn bng FAT va c 1 phn t C mang gi tr 0. -Bc 6: iu chnh li gi tr phn t trn thnh EOF. -Bc 7: a vo entry th mc tm c bc 3 tn & cc thuc tnh ca tp tin (trng cluster bt u c gn gi tr l C) -Bc 8: Lu li entry va iu chnh vo RDET ca a. -Bc 9: Lu li phn t va iu chnh bc 6 vo cc bng FAT ca a. -Bc 10: To 1 vng m c kch thc bng SC v a vo vng m ni dung ca bng th mc con tng ng vi 1 th mc rng (2 entry u c tn l . v .., cc entry cn li u mang gi tr 0. -Bc 11: Lu vng m vo cluster C ca a.4.4 a 1 tp tin bnh thng vo 1 th mc con ca a4.4.1 Thut gii:(u vo: tn a, ng dn n ni cha tp tin, tn & cc thuc tnh ca tp tin, ni dungtp tin; u ra: tn, cc thuc tnh & ni dung tp tin c lu vo a ng ch & ng cutrc lu tr thit k - khng nh hng n cc ni dung ang c sn trn a) Bc 0: Phn tch ng dn xc nh s cp (gi s l N) & tn ca cc th mc con cc cp. Bc 1: c BootSector ca a xc nh cc thng s cn thit (v tr & kch thc ca bng th mc gc & bng qun l cluster, kch thc cluster, v tr bt u ca vng d liu,...) Bc 2: c bng th mc gc vo b nh. Bc 3: c bng qun l cluster vo b nh. Bc 4: Bt u t bng th mc gc ln lt suy ra cc bng th mc con cc cp k tip & cui cng c bng th mc con cha entry ca tp tin (th mc con cp N) Bc 5: Tm trn bng th mc cp N trn 1 entry trng (nu khng c th ni thm 1 cluster trng vo ni dung bng th mc trn).* Bc 6: T kch thc tp tin & kch thc cluster xc nh s cluster N m tp tin phi chim (= /) Bc 7: Tm trn bng qun l cluster c c bc 3 N phn t tng ng vi trng thi cluster trng (nu khng c N phn t th thng bo khng dung lng trng lu ni dung tp tin & thot) Bc 8: iu chnh li gi tr N phn t trn thnh trng thi ca cluster cha ni dung tp tin (theo ng th t ) Bc 9: a vo entry th mc tm c bc 5 tn & cc thuc tnh ca tp tin. Bc 10: Lu li entry va iu chnh vo bng th mc con cp N trn. Bc 11: Lu li bng qun l cluster vo a. 32 33. Bc 12: Phn ni dung tp tin ra thnh nhng phn c kch thc bng kch thc cluster v lu chng vo N cluster tng ng vi N phn t tm c bc 6.4.4.2 a mt tp tin vo 1 th mc con ca a c kin trc FAT12 /FAT16 -Bc 0: Phn tch ng dn xc nh s cp N & tn cc th mc con cc cp. -Bc 1: c BootSector xc nh cc thng s SB, SF, SR, SC, SS. -Bc 2: c bng RDET vo b nh. -Bc 3: c bng FAT vo mng aFAT trn b nh. -Bc 4: Bt u t RDET ln lt suy ra cc SDET cc cp k tip cho n khi c SDET ca th mc con cp N -Bc 5: Tm trn bng SDET trn 1 entry trng (nu khng c th ni thm 1 cluster trng vo ni dung bng th mc trn). -Bc 6: Xc nh s cluster N m tp tin s chim ( N=/SC). -Bc 7: Tm trn mng aFAT N phn t f1, f2, ..., fN c gi tr 0 (nu khng c N phn t th thng bo khng dung lng trng lu ni dung tp tin & thot). -Bc 8: iu chnh li gi tr N phn t trn theo cng thc: aFAT [ fi ] = fi+1, vi i t 1 n (n-1), v aFAT [ fN ] = EOF. -Bc 9: a vo entry th mc tm c bc 5 tn & cc thuc tnh ca tp tin (trng cluster bt u c gn gi tr f1) -Bc 10: Lu li entry va iu chnh vo SDET ca th mc con cp N trn. -Bc 11: Lu li mng aFAT trn vo nF bng FAT trn a. -Bc 12: Phn vng ni dung tp tin ra thnh nhng on c kch thc bng SC v lu chng vo cc cluster tng ng mang ch s f1, f2, ..., fN trn vng DATA.4.5 To mt th mc trong mt th mc con c sn4.5.1 Thut gii:(u vo: tn a, ng dn n ni th mc con c sn, tn & cc thuc tnh ca th mccon cn to; u ra: mt th mc rng c to ra trong th mc con ch ra theo ngcu trc lu tr thit k - khng nh hng n cc ni dung ang c sn trn a) Bc 0: Phn tch ng dn xc nh s cp (gi s l N) & tn ca cc th mc con cc cp. Bc 1: c BootSector ca a xc nh cc thng s cn thit (v tr & kch thc ca bng th mc gc & bng qun l cluster, kch thc cluster, v tr bt u ca vng d liu,...) Bc 2: c bng th mc gc vo b nh. Bc 3: c bng qun l cluster vo b nh. Bc 4: Bt u t bng th mc gc ln lt suy ra cc bng th mc con cc cp k tip & cui cng c bng th mc con cha entry ca tp tin (th mc con cp N) Bc 5: Tm trn bng th mc hin ti 1 entry trng. Bc 6: Tm trn bng qun l cluster 1 phn t tng ng vi trng thi cluster trng. Bc 7: iu chnh li gi tr phn t trn thnh trng thi ca cluster cha ni dung tp tin (v l cluster cui) Bc 8: a vo entry th mc tm c bc 5 tn & cc thuc tnh ca tp tin th mc. Bc 9: Lu li entry va iu chnh vo bng th mc con hin ti. 33 34. Bc 10: Lu li phn t va iu chnh bc 7 vo bng qun l cluster ca a. Bc 11: To 1 vng m c kch thc bng kch thc cluster v a vo vng m ni dung ca bng th mc con tng ng vi 1 th mc rng Bc 12: Lu vng m trn vo cluster tng ng vi phn t tm c bc 6.4.5.2 To th mc trong 1 th mc con ca a c kin trc FAT12 /FAT16 -Bc 0: Phn tch ng dn xc nh s cp N & tn cc th mc con cc cp. -Bc 1: c BootSector xc nh cc thng s SB, SF, SR, SC, SS. -Bc 2: c bng RDET vo b nh. -Bc 3: c bng FAT vo mng aFAT trn b nh. -Bc 4: Bt u t RDET ln lt suy ra cc SDET cc cp k tip cho n khi c SDET ca th mc con cp N -Bc 5: Tm trn bng SDET trn 1 entry trng (nu khng c th ni thm 1 cluster trng vo ni dung bng th mc trn). -Bc 6: Tm trn mng aFAT va c 1 phn t C mang gi tr 0. -Bc 7: iu chnh li gi tr phn t trn thnh EOF. -Bc 8: a vo entry th mc tm c bc 5 tn & cc thuc tnh ca tp tin (trng cluster bt u c gn gi tr l C) -Bc 9: Lu li entry va iu chnh vo SDET ca th mc con cp N trn. -Bc 10: Lu li phn t va iu chnh bc 7 vo cc bng FAT ca a. -Bc 11: To 1 vng m c kch thc bng SC v a vo vng m ni dung ca bng th mc con tng ng vi 1 th mc rng (2 entry u c tn l . v .., cc entry cn li u mang gi tr 0. -Bc 11: Lu vng m vo cluster C ca a. IV. Phc hi nguyn trang khi b xo nhm hoc format nhm .1. Cu d liu b mtKhi bn xa mt tp tin hay th mc no trong h thng, thc cht lnh ny ch nh du" xa" trong Directory Entry v nhng thng tin lin quan trong File Allocation Table - FAT(vi phn vng nh dng FAT/FAT32) hoc nh du "xo trong Master File Table - MFTEntry (vi phn vng nh dng NTFS). Lc ny, cc vng (cluster) cha d liu ca tp tinxem nh trng v c tnh l dung lng cha dng n ca a cng mc d d liu vntn ti. Khi d liu mi c ghi vo, lc ny d liu c mi thc s b xa i v ghi bngd liu mi. Chng ta (v c h iu hnh) u khng th "nhn" thy c nhng d liu bnh du xa nhng nhng phn mm cu d liu vn nhn thy chng khi qut qua b mta. V vy chng ta mi cn n nhng phn mm ny trong vic khi phc d liu.C rt nhiu phn mm gip bn thc hin vic ny, t min ph cho n c ph nhOntrack Easy Recovery, Winternals Disk Commander, Active Uneraser, PC Inspector FileRecovery, Drive Rescue... Mi phn mm u c nhng im mnh - yu ring, nhng nhnchung, kh nng "cu h" ty thuc rt nhiu vo cu trc d liu trn a cng v nhngthao tc c nh hng n cc vng d liu.2. Cu trc d liu trn aTrc tin, chng ta cng tham kho qua cch thc thng tin ca mt tp tin c lu trtrn a cng. Vi phn vng FAT, d liu c lu tr ti 3 ni trn a cng, bao gm:Directory Entry cha thng tin v tp tin gm tn, dung lng, thi gian to v s hiucluster u tin cha d liu ca tp tin; FAT cha s hiu cc cluster c s dng cho 34 35. tp tin v cc cluster cha d liu ca tp tin (vng Allocation). Vi phn vng NTFS, d liuc lu tr trong MFT (Master File Table) Entry v vng Allocation (hnh minh ha).Bt k phn mm cu d liu no cng c gng tm li nhng thng tin t 3 ni ny cth khi phc y ni dung ca mt tp tin, nu thiu (hoc mt) mt trong nhng thngtin ny, d liu khng ton vn hoc khng th khi phc (xem bng).Nh vy, xem xt cc trng hp trn th kh nng khi phc d liu thng kh thp.Trng hp cc cluster ca Allocation b hng hoc b chp , bn hu nh khng th khiphc c v d liu b xa v chp bi d liu mi. V l thuyt, bn vn c th lyli d liu c vi k thut MFM (Magnetic Force Microscope) tuy nhin k thut ny khngc p dng rng ri trn thc t v mt nhiu thi gian v chi ph rt cao. Directory Allocation FAT EntryTp tin c khi phc y Tp tin c khi phc nhng c th ni dung-khng y hoc khng th c c. -Tp tin c th c khi phc nhng khng y- thng tin -Khng th khi phc d vn c th nhn thy tn -- ca tp tin. - -Khng th khi phc v khng cn du vt ca - -- tp tin AllocationMFTTp tin c khi phc y Tp tin c th c khi phc nhng khng y -thng tinKhng th khi phc d vn c th nhn thy tn ca tp -tin. - -Khng th khi phc v khng cn du vt ca tp tin3. Kh nng phc hi d liu- Tp tin b xa: Nh cp trn, vic xa tp tin s nh du xa trong Director Entryv nhng thng tin lin quan trong bng FAT hoc MFT Entry. V l thuyt, kh nng khiphc y tp tin ny l cao. Tuy nhin, kt qu thc t i khi khng c nh mong iv mt s nguyn nhn: sau khi xa, ngi dng c gng thc hin mt s thao tc nhm lyli d liu, HH ghi d liu mi vo cc cluster c nh du xa...- Phn vng b xa (hoc to li) nhng cha nh dng (format): Hu ht d liu u c thkhi phc c trong trng hp ny v FAT v MFT khng b nh hng khi ngi dngxa v to mi phn vng. 35 36. - Phn vng b format: Vi phn vng FAT, vic nh dng s xa bng FAT, Boot Record vth mc gc (Root Directory) nhng Partition Table v d liu trong Allocation vn cn.Nhng tp tin c dung lng nh hn kch thc mt cluster (32KB, mc nh ca FAT32hoc theo ty chn ca bn khi nh dng), tp tin c khi phc hon ton v chng khngcn n thng tin trong bng FAT. Vi nhng tp tin c dung lng ln, nhiu cluster lintip nhau, chng s b phn mnh khi c s thay i ni dung theo thi gian. Vic tm v rpcc cluster c lin quan vi nhau l cng vic kh khn, nht l vi nhng tp tin c dunglng ln v hay thay i. Mt s phn mm cu d liu c kh nng khi phc m khngcn thng tin t bng FAT. tuy nhin, ni dung nhng tp tin sau khi tm li s khng y hoc khng th c c. V vy, bn s cn n mt phn mm c kh nng trch xutnhng ni dung cn c c t nhng tp tin ny (chng ti s cp n vn nytrong bi vit khc khi iu kin cho php). Vi phn vng NTFS, vic nh dng s to MFTmi, tuy nhin kt qu khi phc s tt hn phn vng FAT v NTFS khng s dng bngFAT xc nh cc cluster cha d liu ca cng tp tin.- Phn vng b format v ci HH mi hoc s dng Ghost: Trng hp ny thc s lkh khn v Directory Entry (FAT), MFT (NTFS) b xa. Gi s bn c 10GB d liu lutr trn phn vng 20GB, phn vng ny b format v chp 5GB d liu mi. Nh vy,bn khng th khi phc nhng d liu b chp m ch c th khi phc d liu t5GB tr v sau.4.Mt s lu Bn c th s dng bt c phn mm no trong "tm vi" ca mnh cu d liu, tuynhin chng ti xin lu mt vi im sau.- Mt s phn mm cho dng th v ch yu cu ngi dng nhp s ng k (license key)khi sao lu nhng d liu cn khi phc. V vy, bn hy tn dng iu ny th qua mt viphn mm tm ra phn mm thch hp nht vi loi d liu ca mnh cn khi phc.- Mt s phn mm cho php to a khi ng v lm vic trong ch MS-DOS. Tuynhin, bn s kh khn hn trong vic chn la nhng d liu cn khi phc. Nu c th,hy ci t phn mm cu d liu trn mt h thng khc v gn a cn khi phc vokhi sn sng.Bn s d dng lm vic hn vi nhng tp tin theo cu trc cy th mc, xem qua ni dungnhng tp tin c th khi phc trc khi mua license key. Lu : ng lo lng khi HHkhng nhn ra a cng cn khi phc, phn mm khi phc s lm vic ny tt hn nutrong BIOS Setup vn nhn dng c cng ny.- Trnh nhng thao tc ghi d liu ln a cng cn khi phc. Sau khi xa, v tr nhngcluster ca tp tin khng c bo v, sn sng cho vic ghi d liu mi. C khi ngidng khng to ra nhng tp tin mi, hot ng ca HH cng nh hng n d liu xa khi to ra nhng tp tin nht k (log) ghi li hot ng ca h thng, ngoi ra, vic truycp Internet s ti v kh nhiu tp tin tm cng c ghi trn a cng. Tt nht bn nnngng ngay vic s dng cng ny, ch gn n vo mt h thng khc sau khi chun bsn sng cho vic cu d liu.- ng chm tr khi cu d liu. Hy hnh ng tht nhanh khi nhn thy sai lm ca mnh,bn s c nhiu c hi ly li c d liu xo mt. Ngoi ra, kh nng khi phc phthuc vo loi d liu. Nu l nhng tp tin hnh, bn c th ly li c 9 trn 10 hnh. Tuynhin, nu l c s d liu (database), bng biu... d ly li c 90% nhng c th chngvn v dng v cu trc c s d liu thng c s lin kt, ph thuc ln nhau.- Mt a cng "cht" nu BIOS hay tin ch qun l a cng khng th nhn dng c. cng cht thng c nhng hin tng l nh khng nghe ting mt quay, pht ra nhngting ng lch cch khi hot ng... y l nhng hng hc vt l ca bo mch iu khin,u c, mt, a t... Hy c gng to bn sao nh ca a cng vi Norton Ghost, Drive 36 37. Image hoc tnh nng tng t ca mt s phn mm cu d liu. Khi a cng gp s c,bn c th ly li d liu t bn sao nh ca a cng.- Nu d liu thc s rt quan trng, bn nn em cng n nhng dch v cu d liu cuy tn kim tra, ng thao tc trn a cng v s nh hng n kh nng khi phc dliu hoc lm tnh hnh thm nghim trng. V d nhin, ci gi phi tr cho vic ny skhng r cht no. Tuy nhin, bn ng trng ch nhiu vo vic cu d liu khi cngcht v vic ny t khi thnh cng.V.Gii thiu mt s phn mm tin ch v phn mm cng c dng saolu v phc hi d liu1. Phn mm tin ch v phn mm cng c dng sao luMt h thng sao lu d liu hon ho nh to nh a cng s gip bn c th phc hinhanh chng khi a cng b li, nhng li yu cu bn phi c a cng th 2 hoc phi sdng nhiu a quang sao lu d liu. Thi gian tt nht to nh a l ngay sau khici t Windows v khi ci t cc ng dng. nh a bao gm mt bn sao ca Windowsv tt c nhng chng trnh c cu hnh theo nhu cu s dng. Tuy nhin, bn cngc th ch sao lu nhng th mc v d liu m i vi bn chng thc s quan trng.a) Phn vng ring cho an ton d liuTheo mc nh, Windows v hu ht cc ng dng u lu tr mc nh cc tp tin trongth mc My Documents. Th mc ny lu tr dng nh ton b nh s, m nhc, video...v cc tp tin khc v lu gi chng vo mt ni d dng sao chp. Nhng tht khngmay, th mc ny li thng nm trn cng phn vng khi ng ca Windows- nn khnng d b tn thng v hay b hng hc rt d xy ra. V vy, to ra mt phn vng lutr cc d liu lun l mt tng hay.To mt phn vng lu d liu s n gin, d dng v an ton hn bi bn c th trnhc ghi chng cc tp tin khi ci t li Windows. y l mt hng gii quyt: Chia acng thnh cc a logic (phn vng) lu tr d liu theo nhng mc ch s dngkhc nhau, C: s dng cho h iu hnh, D: cho lu tr ng dng, E: lu tr ccd liu v ti chnh, kinh doanh... v phn vng F: lu tr nh s, cc tp tin m thanh vvideo. c th to phn vng a cng n gin hy s dng Partition Magic 8 ca Symantechay Disk Director Suite ca Acronis. Nhng tin ch ny gip cho qu trnh phn vng acng tr nn n gin, nhanh chng v khng lm mt d liu trn a cng.Nu khng c iu kin cng nh kinh nghim c th s dng cc cng c trn, bn vnc th s dng My Documents nh l trung tm lu tr cc d liu c nhn. Bn c th chnh ng dn cho My Documents vo th mc no trn phn vng khc. M WindowsExplorer, nhn phm phi vo My Documents, la chn Properties, chn nt Move trong thTarget, v duyt ti th mc mun chn. Cui cng, nhn OK hon thnh. 37 38. Hnh 2.10. thay i th mc mc nh ca Outlook Express lu tr email. M chng trnh ny, nhn vo Tools->Options->Maintenance->Store Folder->Change, la chn th mc cha nhng email, v nhn Ok ng li.b) La chn phng tin sao lu thch hpMt yu t rt quan trng ca sao lu d liu l lu tr nhiu bn sao vo nhiu ni khcnhau - bi v cc phng tin sao lu c th b hng hc v bn cng khng mun mtnhng tp tin quan trng. V vy, sao lu vi bn sao trong CD/DVD hay cc phng tinsao lu khc l cn thit, an ton v khng lng ph.Tuy nhin, bn cng phi la chn gii php sao lu d liu cho thch hp. V d: nu cctp tin cn sao lu ln ti 2 GB v bn mun lu tr 3 bn sao ring bit? Chc chn rng,bn khng th sao lu trn mt a CD duy nht, v cng mt rt nhiu thi gian ti lnmy ch Web. Gii php s dng thch hp trong trng hp ny l DVD v cng gnngoi. Ngc li, vi d liu khong 200 MB th sao lu d liu trn CD hoc sao lu trctuyn li l gii php ti u nht.i vi nhiu ngi, DVD l phng tin sao lu d liu c chn. Gi ca nhng aDVD ghi c cng gim gi ng k, v dung lng ca DVD c th lu tr ln hn viln so vi a CD. Hn na cc a DVD c th ghi li cng r hn, v c sn.Nu tm kim cc thit b sao lu d liu m khng cn yu cu tho lp a, hy s dngcc cng gn ngoi nh Media Center ca Western Digital, cho dung lng 250 GB, hocOneTouch ca Maxtor vi dung lng 300 GB.Nhng dch v sao lu d liu trc tuyn nh XDrive v Ibackup th li c gi c tng icao vi 10 USD/thng. Mc d nhng dch v ny cng cho php dng th, v chng chthch hp vi kt ni bng thng rng. Mt iu cn lu l sao lu d liu trc tuyn khan ton, cc dch v ny cung cp bo mt d liu kh tt.Cui cng, phng php sao lu d liu gi cao khc l s dng th nh USB Flash. Saolu bng th nh c kch thc nh gn nhng c dung lng lu tr nh ch khong 1 GB la chn c phng tin sao lu thch hp, bn c th tham kho bng sau: GiKiu sao Khuyn u imKhuyt im Tc thnh/Th thutludng GB - Gn nh v - Dung lng sao- Tc KhongPhc v Vi mc ch n nh. lu ch mc khong t 10 ti cho sao lu s dng hngtrung bnh. 3 MBps 20 cent/hng ngy ngy, CD-CD/DVD - L phng tin sao lu - Khng phi l cho nGB700 MB choRW s l r ph bin, c la chn khi sao12 CD v 4.7 nht v hp sn v khng lu d liu y . MBps.GBcho dn nht. t. - Cng DVD.- L phng tin - D dng khitng i nhynn ch cn di chuyncm vi nhit ti thiv nh nng mt gian38 39. tri. thmcho troi a- Tng i - Kh nng chng Tc 1 Khng nn a cng a nhanh.shock v chu t10 USD/GB s dng vi vi qut lmcng- Dung lngnhit km. MBps ti mcch mt c thgn lu tr ln.- t tin 30 MBpssao lu cc gip bnngoi dliutrnh c- H tr saohng ngy mt mt dlu t ng,cho ngi liu do quc th cms dng gia nng.nng.nh v vnphng nh.- D dng khi Dung lng b gii1 MBps Gi30Sao lu dS dng nTh nh di chuyn hn (USB USD tiliu phc vgin, nn ccUSB - Kch thc1.1) n 100cho di ng tp tin saoFlash nh gn 12 MBpsUSD/GB v trao i lu gip tit(USBd liu kim thm2.0)dung lngtrng, m bnvn c thgii nn bngWindowsExplorer.Rt an ton,Gi tng i cao PhGi t 2 Hu ch khi Hy s dngSao lu bo mt tt,v chm. c bit thucUSD tisaolukt ni bngd liu kh nng saovi cn phi c kt vo tc10 USD/nhng dthng rng vtrclu t ng ni bng thng ca GB/liu nh v ch lu trtuyn n gin, rng khi s dngkt ni. thngcnthit, nhngdchia s tp tin dch v ny.saoluliu thc sn gin. mang tnh quan trng.cht ding, chias cc tptin.- Dung lng- a c bng 1 MBps 25 n ThigianLa chn ttlu tr ca t t v tng n 10 50 cent/ sao lu di.nht khi sphng tin i chm. MBps GB Sao lu ddng giiBng tsoa lu ny - Bng t nhyliu hng php sao lukhng t.cm vi in t.tun chony chng- C khnhng vn sao lu ton- Khng c hnng di phng nh.b d liutr tt i vi mtchuynvo ban m.s phn mm saoluc) Chin lc sao lu hiu qu nhtBc 1: Hy cn nhc v la chn sao lu nhng tp tin, d liu quan trng.Bc 2: Chy cc phn mm sao lu, v la chn cc phn vng, cc tp tin th mc chomc ch sao lu m bn mun bo v. ng qu bn tm vo nhng nhng d liu nh39 40. email, s a ch, v lch... Nu khng chc chn, nhng d liu no cn c sao lu, hym cc ng dng thch hp v tm kim nhng thit lp, la chn trong cc chng trnh.Bc 3: Bo v mt khu v m ho d liu bo v quyn ring t l hon ton cnthit. Hn na, hy a thm nhng m t v bn sao lu , nh "y l bn sao lu ngy12.1.2006.bak" ...Nhng ch thch nh th ny s gip cho bn d nh hn. Tit kimkhng gian lu tr bng cch nn nhng tp tin sao lu cng l gii php hay.Bc 4: S dng cc ng dng kim tra chc nng sao d liu c lm vic mt cchhon ho v chnh xc hay khng l tht s cn thit. iu ny gip bn trnh khi "nhcu" khi s dng bn sao lu b hng v khng th phc hi li c. An ton hn, hy sdng 2 bn sao lu. ( Sao chp t a DVD hoc CD th nht sang a th 2 s nhanhchng v tit kim thi gian hn rt nhiu l s dng tin ch sao lu d liu 2 ln.).Bc 5: Sau khi to mt bn sao lu d liu y (baseline backup), bn c th gimti a thi gian v dung lng trng cn thit bi cch s dng sao lu khc bit (differentialbackup). Cch sao lu ny ch ly nhng d liu c thay i k t ln sao lu d liuy .Kiu sao lu d liu tng dn (incremental backup) cho tc nhanh v cn t dung lnga cng hn. Nhng to li cc tp tin t nhng bn sao lu ny cn phi phc hi ccbn sao lu theo ng th t. Cui cng, khng nn ghi ln bn sao lu d liu y (baseline), bn ch nn ghi nhng bn sao lu khc bit (differential) hoc sao lu tngdn (incremental) sau khi to mt bn sao lu d liu y c cha cng mt ni dungd liu.*NTI Shadow 2.0NTI Shadow 2.0 l mt cng c sao lu d liu hon ho.Shadow l cng c sao lu lin tc: Khng ging nh cc phn mm sao lu truyn thngkhc, Shadow cho php sao lu d liu nhanh chng m khng cn phi t lch sao luhng ngy hoc hng gi. Mi ln bn lu mt tp tin vo a cng, Shadow s to ngaybn sao th 2. Chnh iu ny lm cho tc sao lu ca chng trnh nhanh hn micng c sao lu khc. Mc d, c kin cho rng phng php ny gy gim tc hthng, nhng qua th nghim th Shadow khng lm thay i ln ti hiu nng h thng,ng thi chng trnh chy cng kh nhanh. Tuy nhin, dung lng sao lu th ln hncc cng c khc.Khi Shadow c ci t v cu hnh, bn c th thit lp sao lu theo mun ca mnh.C th yu cu sao lu nhng tp tin, th mc h thng no v lu tr chng vo ni bnmun. Nu my tnh ang s dng c kt ni mng, bn c th lu cc bn sao lu trn a mng. Nu khng, ngi dng c th a tt c d liu ny sang thit b lu tr ngoinh: cng ngoi, USB...Khi thit lp ch sao lu trn USB, ng dng thngminh pht hin ra cc thit b USB c kt ni vo hthng. Tnh nng thng minh ny c NTI gi l SmartUSB Device Detection, ng dng cng s dng sao lu khic thit b USB khc c kt ni.Bn cng c th lc cc tp tin cn sao lu, cu hnh saolu nhng kiu, loi ti liu cn thit nh: Word, Excel,pdf.... Shadow cn c tnh nng "c nht v nh", cho phpsao lu nhiu bn sa i ca mt ti liu. Chng hn, bnlu (Save) cc chnh sa mt vn bn Word 10 ln, lc bn s c 10 bn sao lu khc nhau ca vn bn ny.Shadow cng a ra nhng cch thc sao lu truyn thngHnh 2.11 khc. My tnh ca bn cng khng cn "tr trung" na, hiunng ca my gim ng k vi phng php sao lu mi40 41. ca NTI. Tt nhin, Shadow c thit lp sao lu vo nhng lc my ang ngh, t lch saolu theo pht, gi, hoc theo ngy.2. Phn mm tin ch v phn mm cng c dng sao lu v phc hi d liuC khng t trng hp, d liu quan trng c th b xa do s "v tnh" ca ngi dng, dovirus hoc rt nhiu nguyn nhn khc na. Khi vic phc hi chng s l u tin hngu v i khi d liu l mt th m tin cng khng th mua c. Sau y l mt s tinch phc hi d liu quan trng* Ultimate Boot CD v2.1Nu chic PC ca bn tr nn "m yu", th ti sao bn khng s dng mt cng c no "khm" cho n? Trong trng hp ny, Ultimate Boot CD s l mt cng c hu ch, chophp bn chy trnh chun on t a CD, ch khng phi l chic cng "bnh tt" camnh. Vi Ultimate Boot CD, bn c th to mt a CD khi ng cho bt c loi cng,chng trnh qun l cng, trnh chun on b nh v a phc hi s c cho HH Linuxno.* ISOBuster v1.5Ngi dng my tnh u bit rng a CD rt hu ch cho cng vic sao lu v phc hi dliu; th nhng v mt s l do no , nhng chic a CD nh th li khng th m c.Vy phi lm th no c th cu vn s d liu sao lu trc . Nu bn tng lmvo hon cnh ny, ISOBuster v1.5 s gip bn phc hi d liu t a CD v DVD. Tin chs kim tra cc vn vt l pht sinh i vi a CD hoc DVD, bin dch li cc danh schfile c cha li c vt l, v cho php bn c th lu li v chnh sa chng. ISOBusterv1.5 cng c th tm cc file b mt v cho php bn m v chnh sa chng.* VirtualLab Data Recovery Software v3.3.5i vi ngi thng xuyn s dng my tnh, vic mt mt d liu khng phi l chuyn hihu m ngc li, rt d xy ra. Nguyn nhn mt mt d liu th c nhiu, nhng tm lich yu do bn format nhm cng, xa th mc hoc d liu b virus tn cng... Trongtrng hp ny, vn ca bn s khng b "bi kch ha" nu bn c trong tay cng cVirtualLab Data Recovery - tin ch hp nht d liu. VirtualLab Data Recovery s kt nimy tnh ca bn ti mt my ch phc hi d liu mnh v s dng chng trnh tr tunhn to phc hi d liu. Trnh phc hi d liu trn tng thch vi cc nh dng FAT12, FAT 16, FAT 32, v NTFS. VirtualLab Data Recovery cng c th tm li d liu t aJaz, Zip v thit b camera s.Ch : Chng trnh ny c cung cp min ph, nhng nu bn dng chng phc hid liu cho my ch, bn s phi tr tin v mc ph s ph thuc vo s lng d liu cnphc hi.* File RecoverBn s cm thy th no nu xa nhm mt file quan trng trn my tnh? Chc hn l skhng n ri! Tuy nhin, bn cng khng cn phi qu "cung" ln v File Recover c thxc nh c cc file b xa trn cng v cho php bn phc hi chng. Tin ch ny squt cc cng vt l v logic trong khong thi gian 1 pht v s cho hin th mt danhsch cc file bn xa. Bn cng c th phc hi cc fle xa trong thng rc. FileRecover h tr cng IDE/ATA/SCSI v cc loi cng ln hn 8GB,Ch : Tic ch File Recover hin ch c cung cp dng dng th, v bn ch c thphc hi 2 file d liu (rt tic!). Bn cn phi tr tin c c phin bn y ca FileRecover.* File ScavengerTin ch ny c th phc hi d liu b xa nhm hoc cc file nm trong phn vng cngb hng. File Scavenger c th truy c cc file b mt k c trong trng hp cng cabn hoc cc phn vng cng b hng, lm cho Windows khng th nhn din c. FileScavenger h tr tt c cc loi cng, k c nh dng nn NTFS.*Norton Disk Doctor trong System Works, Scandisk ca Windows 98, Chkdsk trong ccphin bn Windows c th xc nh cc cung t (sector) b hng v chuyn cc d liu ca41 42. bn sang cc cung t "kho mnh", ng thi nh du cc cung t b hng, nhm trnh ghid liu vo cung t . Tuy nhin, cc tin ch ny khng phc hi c nhiu d liu.*EasyRecovery Lite khng ch phc hi cc tp tin b mt, n cng c th phc v sa chaphn no cc tp tin b li nh Word v Zip. EasyRecovery Lite c ch tm kim phchi d liu dng gc (RawRecovery) cng hng, khi mkhng c th mc no tn ti.EasyRecovery Lite cn c tnh nng hp dn hn, chngtrnh ny c th phc hi cc tp tin sau khi cng bnh dng li (format). Trong ch ny, EasyRecovery squt rt chm a cng. Chng trnh ny c th chy ta mm khi ng hoc chy t a CD ci t. BnEasyRecovery Lite gii hn phc hi 25 tp tin trong miphin lm vic. Nu bn cn ly li nhiu hn 25 tp tin hoch tr nhiu kiu tp tin.Hnh 2.12Cu hi v bi tp:1- Cu trc ca th mc v tp tin trn my n c t chc nh th no?2- Trnh by cch thc lu tr d liu qua bng FAT.3- Thc hin qui trnh nh dng a cng, a mm, a Flash4- Ci t v s dng phn mm tin ch v phn mm cng c dng sao lu v phc hi d liu : UltimateBoot CD v2.1, ISOBuster v1.5, VirtualLab Data Recovery Software v3.3.5, File Recover, Norton Disk Doctor,EasyRecovery Lite42 43. BI 3 Tn bi : VIRUS TIN HC V CC PHNG CHNG M bi : ITPRG03-19.3Gii thiu : Bi hc cung cp cc kin thc v tnh nng ca Virus tin hc, cch hot ngca virus v s dng mt s phn mm dit virus. Virus my tnh l mt chng trnh phnmm v chng trnh ny c thit k c th ly lan ra cc file chng trnh hoc cckhu vc h thng ca a cng hay a mm, c im c trng ca chng l kh nng tnhn bn.Virus lun lun c th t nh lm mi vic m khng cn c s cho php cangi s dng, nhng tt nhin l ln u tin phi c mt thao tc no ca ngi sdng kch hot n ln (do khng bit l virus).Mc tiu thc hin:- Hiu c cc tnh nng ca Virus tin hc, cch hot ng ca virus v s dng mt sphn mm dit virus .Ni dung chnh:3.1 Gii thiu v cc loi Virus tin hc .Virus my tnh l g? Thut ng ny ch mt chng trnh my tnh c th t sao chp chnh n ln nhng a, file khc m ngoi s dng khng hay bit. Thng thng virus my tnh mang tnh cht ph hoi, n s gy ra li thi hnh, lch lc hay hy d liu. Chng c cc tnh cht: Kch thc nh Tnh lay lan: cc chng trnh ny c tnh cht lay lan t chng trnh sang chng trnh khc, t a ny sang a khc v do lay t my ny sang my khc Tnh ph hoi: i khi ch l nhng cu tru a, hay nguy him hn chng s tiu dit v ph hy cc chng trnh v d liu.Tn VirusTn cc loi virus l do nhng nh pht trin phn mm dit virus t, n c th da theoc dim k thut ca virus, cc ni dung lin quan n virus hoc da theo c im phhoi, thi im ly nhim... Tm li l mi phn mm dit virus c th t tn virus theo cchca ring mnh. Nh vy, cng mt virus c th c nhiu tn khc nhau. V d : Vi loi virusBkav gi l W32.Magistr.B th chng trnh Norton AntiVirus li gi l W32.Magistr.Corrupt.Khi nhc n tn ca virus th bn cn phi cung cp thm thng tin l ci tn do phnmm dit virus no t.Ngy nay th bn thng thy tn cc virus c ch W32 u, iu c ngha l virus nyly lan trn h iu hnh Windows 32bit. Thc ra iu ny hin nay rt t ngha, n ch c ngha khi m vi nm trc y mi ngi cn s dng h iu hnh Windows 16bit, cncc h iu hnh Windows ph bin hin nay u l Windows 32bit cho nn cc virus hinnhin s l loi ly trn Windows 32bit v c tn l W32.xxx Tt nhin vic t tn ny lkhng bt buc m do cc hng pht trin phn mm dit virus ngm quy c vi nhau.Kch thcVirus my tnh vo nhng nm 90 thng ly vo cc file chng trnh v lm cho cc fileny b tng kch thc ln. Ngi s dng pht hin ra my ca mnh nhim virus khi thymt s file b tng kch thc ln mt lng c nh no . Chnh v vy, thng tin v kchthc ca virus c th gip h nhn ra c loi virus ang ly trn my ca mnh. Tuynhin ngy nay cc loi virus thin bin vn ho rt nhiu v nh vy thng tin v kch thcca chng gn nh khng cn ngha. 43 44. Loi fileCng ging nh trn, ngy nay virus ly lan vi bt k loi file no, v vy thng tin v loifile cng khng cn quan trng nh trc y, v c l bn cng khng cn phi quan tmnhiu n thng tin ny.Tuy nhin c mt s loi virus bn s thy thng tin trong mc ny ghi l Worm, Trojan haySpyware, Adware. iu ny ni rng loi virus l su my tnh (Worm) hay phn mmgin ip (Trojan, Spyware, Adware).Worm: Loi virus ly t my tnh ny sang my tnh khc qua mng, khc vi loi virustruyn thng trc y ch ly trong ni b mt my tnh v n ch ly sang my khc khi ai em chng trnh nhim virus sang my ny.Trojan, Spyware, Adware: L nhng phn mm c gi l phn mm gin ip, chngkhng ly lan nh virus. Thng bng cch no (la o ngi s dng thng qua mttrang web, hoc mt ngi c tnh gi n cho ngi khc) ci t v nm vng ti my cann nhn, t chng gi cc thng tin ly c ra bn ngoi hoc hin ln cc qung congoi mun ca nn nhn.3.2 Cc tnh nng ca Virus tin hcThng thng, da vo i tng ly lan l file hay a m virus c chia thnh hai nhmchnh- B-virus: Virus ch tn cng ln Master Boot hay Boot Sector.- F-virus: Virus ch tn cng ln cc file thc thi ( *.com, *.exe )Mc d vy, cch phn chia ny cng khng hn l chnh xc. Ngoi l vn c cc virus vatn cng ln Master Boot (Boot Sector) va tn cng ln file kh thi. c mt cch nhn tng quan v virus, chng ta xem chng dnh quyn iu khin nhth no.a.B-virus.Khi my tnh bt u khi ng (Power on), cc thanh ghi phn on u c t v0FFFFh, cn mi thanh ghi khc u c t v 0. Nh vy, quyn iu khin ban uc trao cho on m ti 0FFFFh: 0h, on m ny thc ra ch l lnh nhy JMP FAR nmt on chng trnh trong ROM, on chng trnh ny thc hin qu trnh POST (PowerOn Self Test - T kim tra khi khi ng).Qu trnh POST s ln lt kim tra cc thanh ghi, kim tra b nh, khi to cc Chip iukhin DMA, b iu khin ngt, b iu khin a... Sau n s d tm cc Card thit bgn thm trao quyn iu khin cho chng t khi to ri ly li quyn iu khin. Ch rng y l on chng trnh trong ROM (Read Only Memory) nn khng th sa i, cngnh khng th chn thm mt on m no khc.Sau qu trnh POST, on chng trnh trong ROM tin hnh c Boot Sector trn a Ahoc Master Boot trn a cng vo RAM (Random Acess Memory) ti a ch 0:7C00h vtrao quyn iu khin cho on m bng lnh JMP FAR 0:7C00h. y l ch m B-virusli dng tn cng vo Boot Sector (Master Boot), ngha l n s thay Boot Sector (MasterBoot) chun bng on m virus, v th quyn iu khin c trao cho virus, n s tinhnh cc hot ng ca mnh trc, ri sau mi tin hnh cc thao tc nh thngthng: c Boot Sector (Master Boot) chun m n ct giu u vo 0:7C00h ri traoquyn iu khin cho on m chun ny, v ngi s dng c cm gic rng my tnh camnh vn hot ng bnh thng.b.F-virus.Khi DOS t chc thi hnh File kh thi (bng chc nng 4Bh ca ngt 21h), n s t chc livng nh, ti File cn thi hnh v trao quyn iu khin cho File . F-virus li dng imny bng cch gn on m ca mnh vo file ng ti v tr m DOS trao quyn iu khincho File sau khi ti vo vng nh. Sau khi F-virus tin hnh xong cc hot ng camnh, n mi sp xp, b tr tr li quyn iu khin cho File cho File li tin hnh hotng bnh thng, v ngi s dng th khng th bit c.Trong cc loi B-virus v F-virus, c mt s loi sau khi dnh c quyn iu khin, s tinhnh ci t mt on m ca mnh trong vng nh RAM nh mt chng trnh thng tr 44 45. (TSR), hoc trong vng nh nm ngoi tm kim sot ca DOS, nhm mc ch kim sotcc ngt quan trng nh ngt 21h, ngt 13h,... Mi khi cc ngt ny c gi, virus s dnhquyn iu khin tin hnh cc hot ng ca mnh trc khi tr li cc ngt chun caDOS.3.3 Cc hnh thc tn ti v ly lanCc c im ca B-VIRUS.Qua phn trc, chng ta a ra cc thng tin ht sc c bn v cu trc a, tin trnhkhi ng v cch thc t chc vng nh, t chc thi hnh file ca DOS. Nhng thng tin gip chng ta tm hiu nhng c im c bn ca virus, t a ra cch phngchng, cha tr trong trng hp my b nhim virus.I. Phn loi B-virus.Nh chng ta bit, sau qu trnh POST, sector u tin trn a A hoc a C c cvo vng nh ti 0: 7C00, v quyn iu khin c trao cho on m trong sector khing ny. B-virus hot ng bng cch thay th on m chun trong sector khi ng nybng on m ca n chim quyn iu khin, sau khi ci t xong mi c sectorkhi ng chun c virus ct gi u vo 0:7C00 v tr li quyn iu khin choon m chun ny. Vic ct gi sector khi ng ti v tr no trn a tu thuc loi a vcch gii quyt ca tng loi virus. i vi a cng, thng thng n c ct gi u trong Side 0, Cylinder 0 v trong c track ny, DOS ch s dng sector u tin cho bngPartition. Trn a mm, v tr ct gi s phc tp hn v mi ch u c kh nng b ghi thng tin. Mt s hng sau y c cc virus p dng:S dng sector cui Root Directory, v n thng t c s dng.S dng cc sector cui cng trn a, v khi phn b vng trng cho file, DOS tm vngtrng t nh n ln cho nn vng ny thng t c s dng.Ghi vo vng trng trn a, nh du trong bng FAT vng ny l vng b hng DOSkhng s dng cp pht na. Cch lm ny an ton hn cc cch lm trn y.Format thm track v ghi vo track va c Format thm.Ty thuc vo ln ca on m virus m B-virus c chia thnh hai loi:a. SB-virus.Chng trnh ca SB-virus ch chim ng mt sector khi ng, cc tc v ca SB-viruskhng nhiu v tng i n gin. Hin nay s cc virus loi ny thng t gp v c l chl cc virus do trong nc "sn xut".b. DB-virus.y l nhng loi virus m on m ca n ln hn 512 byte (thng thy).V th m chng trnh virus c chia thnh hai phn:- Phn u virus: c ci t trong sector khi ng chim quyn iu hin khi quyniu khin c trao cho sector khi ng ny. Nhim v duy nht ca phn u l: ti tipphn thn ca virus vo vng nh v trao quyn iu khin cho phn thn . V nhim vn gin nh vy nn phn u ca virus thng rt ngn, v cng ngn cng tt v cngngn th s khc bit gia sector khi ng chun v sector khi ng b nhim viruscng t, gim kh nng b nghi ng.- Phn thn virus: L phn chng trnh chnh ca virus. Sau khi c phn u ti vovng nh v trao quyn, phn thn ny s tin hnh cc tc v ca mnh, sau khi tin hnhxong mi c sector khi ng chun vo vng nh v trao quyn cho n my tnh lmvic mt cch bnh thng nh cha c g xy ra c.II. Mt s k thut c bn ca B-virus.D l SB-virus hay DB-virus, nhng tn ti v ly lan, chng u c mt s cc k thutc bn nh sau:a. K thut kim tra tnh duy nht.Virus phi tn ti trong b nh cng nh trn a, song s tn ti qu nhiu bn sao ca 45 46. chnh n trn a v trong b nh s ch lm chm qu trnh Boot my, cng nh chim qunhiu vng nh nh hng ti vic ti v thi hnh cc chng trnh khc ng thi cnglm gim tc truy xut a. Chnh v th, k thut ny l mt yu cu nghim ngt vi B-virus.Vic kim tra trn a c hai yu t nh hng:Th nht l thi gian kim