Chapter 6 – External MemoryMagneticDisk

Group # 6

•Ramon Canseco•Jorge Mora•Ibrahim Babun•Dominic Tang How•Bao Kun•Ricardo Gonzalez

What is a Magnetic disk?Circular platter constructed of non-

magnetic material, the material is called substrate, coated with a magnetizable material.

Recently the use of glass substrate have introduce the following benefits:◦Improve uniformity of the magnetic film,

to increase reliability.◦Reduces read-write errors◦Better stiffness to reduce disk Dynamics◦Greater ability to withstand shock and

damge.

Key points of magnetic diskRemain the most

important component of external memory.

Used in system raging from personal computer to super computer.

Both removable and fixed, or hard disk.

For greater performance and larger server system a RAID disk is used. Also later on, you will learn about optical storage.

Magnetic disk write mechanismData are recorded on and later

retrieved from the disk via a conducting coil named the head.◦In many system there are two

heads: A read head and a write head.

During the write mechanism the head is stationary while the patter rotates beneath it.

Write mechanismElectricity flows through a coil

that produces a magnetic filed.Electric pulses are sent to the

write head:◦Resulting in the magnetic patterns

recorded.

Data Organization and Formatting

Tracks are a concentric set of rings on the platter.

Tracks are separated by Gaps. Gaps prevent errors

due to misaligned heads. Sectors is how data is

transferred to and from disk.

Constant Angular velocity is the disk at a fixed speed.

Constant Angular Velocity

Advantage: Disadvantage:

The advantage of using CAV is that individual blocks of data can be directly addressed by track and sector.

The disadvantage of CAV is that the amount of data that can be stored on the long outer tracks is the only same as what can be stored on theshort inner tracks.

Physical Characteristics

A removable disk can be removed and replaced with another disk.

A non-removable disk is permanently mounted in the disk drive; the hard disk in a personal computer is a non-removable disk.

Movable-head disk, there is only one read-write head.

Winchester Disk Format(Seagate ST506)

•The ST-506 was the first 5.25 inch hard disk drive.•Introduced in 1980 by Seagate Technology•It stores up to 5 megabytes after formatting and cost $1500

•The term Winchester was originally used by IBM as a code name for the 3340 disk model prior to its announcement. •The 3340 was a removable disk pack with the heads sealed within the pack. The term is now applied to any sealed-unit disk drive with aerodynamic head design. The Winchester disk is commonly found and built into personal computers and workstations, where it is referred to as a hard disk.

Disk Performance ParametersT = b/rNWhere :

◦ T transfer time◦ b number of bytes to be transferred◦ N number of bytes on a track◦ r rotation speed, in revolutions per second

Thus the total average access time can be expressed as

Ta = Ts + 1 /(2r) + b/rNWhere Ts is the average seek time.

Size/Performance/Uses differs

What is Raid???

RAID(Redundant Array of Independent Disks )

-RAID is a technology that provides increased storage functions and reliability through redundancy.

- The RAID scheme consists of seven levels, zero through six.

- The RAID strategy employs multiple disk drives

RAID 0 (also known as a stripe set or striped volume)

Following are the key points to remember for RAID level 0.

- Minimum 2 disks.

- Excellent performance ( as blocks are striped ).

- No redundancy ( no mirror, no parity ).

- Don’t use this for any critical system.

RAID 1

Following are the key points to remember for RAID level 1.

- Minimum 2 disks.

- Good performance ( no striping. no parity ).

- Excellent redundancy ( as blocks are mirrored ).

the important aspect of this RAID is that information on one

disk or partition is being replicated.

RAID 2(bit-level striping with dedicated Hamming-code parity) RAID 2 requires fewer disks than RAID 1

A RAID 2 stripes data at the bit (rather than block)

uses Hamming code for error correction

The use of Hamming code permits using 7 disks in RAID 2

Because of its high cost and complexity, RAID 2 never really

caught on

RAID 3byte-level striping with dedicated

parityonly a single redundant diskparallel access with small strips

of dataReconstruction of parity disks

RAID 3

Advantages Disadvantages

Very high read and write data transfer rate

Insignificance impact from disk failure

Efficient low ratio of parity disks to data

Transaction rate equals to single disk drive

Complex controller design

RAID 4block-level striping with dedicated

parityindependent access arrayallows I/O requests to be performedstrips are relatively largebit-by-bit parity strip is calculated

RAID 4

Advantages Disadvantages

Very high read data transaction rate

Efficient low ratio of parity disks to data

Quite complex controller design

Worst write transaction and write aggregate transfer rates

Difficult and inefficient data rebuild

RAID 5block-level striping with

distributed paritydistributes the parity strips

across all disksround-robin schemeavoids the bottleneck found in

RAID 4.

RAID 5

Advantages Disadvantages

Highest read data transaction rate

Good aggregate transfer rate

Efficient low ratio of parity disks to data

The most complex controller design

Difficult to rebuild during disk failure

RAID 6block-level striping with double

distributed paritytwo different parity calculations stored in separate blocks on different

disksextremely high data availability

RAID 5

Advantages Disadvantages

Extremely high data fault tolerance

Sustain multiple simultaneous drive failures

More complex controller design

Controller overhead is extremely high

Optical Memory

Optical Disk ProductsCD

◦CD-ROM; CD-R; CD-RW;

DVD◦DVD-R; DVD-RW

Blu-Ray

CD Operation

Basic One-Side Disc Operation

Double-Sided Disc Operation

CD-ROM Block Format

SYNC: Identifies the beginning of a block.

Header: Contains the block address and the mode byte.Mode 0: Specifies a blank data fieldMode 1: Specifies the use of error-correction= 2048 bytesMode 2: Specifies 2336 bytes of user data with no error correcting code.

Auxiliary: Additional user data in mode 2. 288 bytes used as error-correcting code in Mode 1

High Definition Optical Disks-Blu Ray:-Same size as CDs and DVD (1.2mm)- Contains 25GB of data per layer-Available with Triple (100GB) and Quadruple (128GB) Layers

-The name Blu-ray refer to blue laser used to -read disc

HD DVD-No longer in production-Lost optical disc war to Blu Ray

Example ofHigh -Definition

QuestionsFor CDs and DVDs, what does,

pits and lands ( no change in elevation) converts to in digital signals?

What was a major factor in the Blu Ray, HD DVD optical disk war?

6.4 MAGNETIC TAPE

Magnetic TapeSequential accessSerpentine recordingVery cheapBackup and archiveLinear Tape-Open (LTO) Tape

Drives◦Developed late 1990s◦Open source alternative to

proprietary tape systems

Linear Serpentine Recording

Access to data

Move from record 1 to N.◦ Read records 1

through N-1 one at a time

If beyond N◦ Rewind tape x

distance and begin reading

Tape Directory◦ Physical tape location

for a given data block◦ Detected while

winding tape

Linear Tape-Open (LTO) Tape Drives

LTO-1 LTO-2 LTO-3 LTO-4 LTO-5 LTO-6

Release date 2000 2003 2005 2007 2010 TBA

Compressed capacity

200 GB 400 GB 800 GB 1600 GB 3 TB 8 TB

Compresses transfer rate (MB/s)

40 80 160 240 280 525

Linear Density (bits.mm)

4880 7198 9638 13300 15142

Tape tracks 384 512 704 896 1280

Tape length 609 m 609 m 680 m 820 m 846 m

Tape width (cm)

1.27 1.27 1.27 1.27 1.27

Write elements

8 8 16 16 16

USB flash driver

Universal Serial Bus—Flash—Driver

Name and DefinitionAs the name of this device, What

USB flash driver is a driver which using flash memory chip as its storage media and communicating with computer or other device via Universal Serial Bus.

Universal Serial Bus it is an industry standard

developed in the mid-1990s that defines the cables, connectors and protocols used for connection, communication and power supply between computers and electronic devices.

Device classes

USB defines class codes used to identify a device’s functionality and to load a device driver based on that functionality. This enables every device driver writer to support devices from different manufacturers that comply with a given class code.Device classes include:

Class Usage Description Examples, or exception

00h Device Unspecified[12]

Device class is unspecified, interface descriptors are used to determine needed drivers

01h Interface Audio Speaker, microphone, sound card, MIDI

02h BothCommunications and CDC Control

Modem, Ethernet adapter, Wi-Fi adapter

03h InterfaceHuman interface device (HID)

Keyboard, mouse, joystick

05h InterfacePhysical Interface Device (PID)

Force feedback joystick

06h Interface Image Webcam, scanner

07h Interface Printer Laser printer, inkjet printer, CNC machine

08hInterface

Mass storageUSB flash drive, memory card reader, digital audio player, digital camera, external drive

09h Device USB hub Full bandwidth hub

0Ah Interface CDC-DataUsed together with class 02h: communications and CDC control

0Bh Interface Smart Card USB smart card reader0Dh Interface Content security Fingerprint reader0Eh Interface Video Webcam0Fh Interface Personal Healthcare Pulse monitor (watch)

DCh Both Diagnostic Device USB compliance testing device

E0h Interface Wireless Controller Bluetooth adapter, Microsoft RNDISEFh Both Miscellaneous ActiveSync device

FEh Interface Application-specificIrDA Bridge, Test & Measurement Class (USBTMC),[13] USB DFU (Direct Firmware update)[14]

FFh Both Vendor-specificIndicates that a device needs vendor specific drivers

USB 1.1 and before；USB 2.0

USB 2.0: Released in April 2000.Added higher maximum bandwidth of 480 Mbit/s (60 MB/s) (now called "Hi-Speed"). Further modifications to the USB specification have been done via Engineering Change Notices (ECN). The most important of these ECNs are included into the USB 2.0 specification package available from USB.org

On-The-Go Supplement 1.3: Released in December 2006.USB On-The-Go makes it possible for two USB devices to communicate with each other without requiring a separate USB host. In practice, one of the USB devices acts as a host for the other device.

• USB 1.0: Released in January 1996.Specified data rates of 1.5 Mbit/s (Low-Bandwidth) and 12 Mbit/s (Full-Bandwidth). Does not allow for extension cables or pass-through monitors (due to timing and power limitations). Few such devices actually made it to market.

• USB 1.1: Released in September 1998.Fixed problems identified in 1.0, mostly relating to hubs. Earliest revision to be widely adopted.

USB 3.0 and futureThere have been many reports of USB 3.0

equipment only transferring data at USB 2.0 speed, usually with a message "This USB Mass Storage Device can transfer information faster if you connect it to a Super-Speed USB 3.0 port". This has been due to several causes, including drivers, certain cables specified as USB 3.0 (problems disappeared when a different cable was used), order of starting equipment, equipment needing to be disconnected and reconnected, and overclocked computers

Flash

Flash memory (either NOR or NAND-type type)  is invented by Dr. Gang Fujio  from Toshiba Corporation in 1984. According to Toshiba Flash  the name "Flash" is  following colleagues suggested.

Because the memory erase process reminded him of the camera's flash.  Dr. Gang Fujio  San Francisco, California in 1984 IEEE International Conference electronic components(International Electron Devices Meeting, IEDM)published the invention. Intel saw the great potential of this invention, and in 1988 launched the first commercial NOR Flash chips

SLCTraditionally, each memory cell stores one bit of

information, called single-stage storage unit(single-level cell, SLC), the use of this storageunit, also known as single-stage flash flashmemory cell (SLC flash memory), or simply SLC flash memory. SLC flash memory has the advantage of faster transmission speed, lower power consumption and memory cells live longer.However, because each memory cell containsless information, it takes a higher per megabytecost to produce. As fast transmission speed, SLC flash technology will be used in high-performance memory card.

MLC Multi-stage flash memory storage unit (Multi-level cell

flash memory, MLC flash memory) can be stored in each memory cell within the two or more bits of information, its "multi-stage" refers to the charge can charge more than one order (ie, more a voltage value), so the value can store multiple bits in each storage unit. Borrow from each memory cell can store more bits, MLC flash memory can reduce production costs, compared with SLC flash, its slow transmission speed, power consumption and high life of the lower storage unit, so the MLC flash memory technology will be used in the standard type of memory card. In addition, the flying cable semiconductor Mirror Bit ® technology, also belong to this type of technology.

References:http://www.computerrepairinvicto

ria.com/images/raidarticle_whatis.gif

http://www.google.com/search?um=1&hl=en&biw=824&bih=830&tbm=isch&sa=1&q=Hard+drive&oq=Hard+drive&aq=f&aqi=g10&aql=&gs_sm=e&gs_upl=6292l8120l0l8580l10l7l0l0l0l0l214l11

http://en.wikipedia.org/wiki/External_Memory_Interface

Hope you enjoyed our presentation!!