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Storage School I

An introduction to the world of storage


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Storage School I:An introduction to the world of storage

Presented by Stephen FoskettDirector of the Data Practice

Contoural

[email protected]
mailto:[email protected]://www.contoural.com/http://www.contoural.com/mailto:[email protected]


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The world of storage can be daunting theuninitiated. This session provides all of the

background that you will need to get started in the

world of storage. We will start with the basicconcepts: SAN vs. NAS, block vs. file, RAID levels,and other basic topics. These are woven together ina lively lesson, explaining how we got here and why

it all matters. We will finish up with a brief

discussion of how storage fits within the big pictureof enterprise IT.


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WHAT I ASSUME YOU KNOW

Storage School I assumes no prior

knowledge of storage topics, but a basiccomprehension of computing and networks

would be helpful.


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BY THE END OF THE SESSION,YOULL KNOW THE FOLLOWING:

A bit of history and context

Five Important Concepts: Storage outside the computer

Blocks and files

The importance of SCSI

What RAID is and why its important The three kinds of storage arrays

How it all fits together in a storage architecture


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How involved with storage are you?1. Im soaking in it! (its my job)

2. Touch and go (Im involved but not all the time)

3. I just stepped in quicksand! (Im new to all this)4. Cardboard boxes and tape! (whats this all about?)


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(There Is Nothing New Under The Sun)

The basic concepts of storage are not newand most are easy to grasp once thereasoning and history behind them isunderstood

Simply put, the storage world of today is theresult of consolidation, networking, andsharing of resources

We mostly talk about open systems now, butmuch of the work was pioneered in the worldof mainframes and minicomputers


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Important Concept #1:Storage is Outside the Computer

Mainframe storage has always been locatedin a separate cabinet IBM introduced the first disk drive system in 1956,

the 350 disk storage unit The storage industry was born with plug-

compatible storage for the System/360s 2311 and2314 DAS in the 1960s

Bus-and-tag became ESCON in 1990 Open systems storage moved outside later

Seagates 1980 introduction of the ST506 broughthard disk storage to the personal computer

Introduced in 1986, SCSI allowed personalcomputers and servers to access external storage

IBM 350

IBM 2314

ST506

ESCON

SCSI


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Were Used to ExternalStorage Today

External disks are common from PCs toservers FireWire and USB storage is used on PCs External Serial ATA (eSATA) is becoming more

common Servers still use SCSI, but also commonly use Fibre

Channel

Networked storage is also gaining attention NAS and iSCSI use common Ethernet and IP

protocols

Enterprise storage generally consists of SCSI,Fibre Channel, and Ethernet

FireWire

and USB

eSATA

Ethernet

FibreChannel


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Important Concept #2:Blocks and Files

Disk drives (and things like disk drives) organizedata in blocks Equal-sized units have unique addresses on the disk

People (and most applications) organize data asfiles in folder hierarchies

Filesystem drivers in the operating system

translate file requests to block addresses


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Most Enterprise Storage Systems andProtocols are Blockor File Based

Block protocols require a filesystem driver in thecomputer to locate files SCSI, Fibre Channel, and iSCSI Also USB, FireWire, thumb drives anything that acts like

a disk drive

File-based devices handle the file translation andorganization themselves File servers and NAS arrays return data based on directory

location and filename

Content-addressable storage (CAS) is somethingelse altogether CAS uses a hash of the content itself (block orfile) to

create a unique address for data


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SAN and NAS

A storage area network (SAN) is a block storage

network SCSI initiators (servers) talk to targets (disks or

arrays) and request access to logical sets of block storage(LUNs)

SAN implies FC or iSCSI storage

Network-attached storage (NAS) is a file storage

network Clients request files from file servers or NAS arrays

(filers) Common NAS protocols include CIFS/SMB for Windows

and NFS for UNIX A network of NAS devices has been dubbed a file area

network (FAN)


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Important Concept #3:Most Enterprise Block Storage Uses SCSI

SCSI is the foundation of all current

enterprise block storage protocols SCSI is both a command set and physicalspecification

Thick parallel SCSI cables of old have beenreplaced by new connections Fibre Channel = SCSI commands over Fibre

Channel Protocol on optical fiber or copper cables iSCSI = SCSI commands over TCP/IP, commonly

over Ethernet SAS = SCSI commands over some FCP services

and a serial transport based on Serial ATA (SATA)

Mainframes now use FICON which is likeESCON over FCP (not SCSI)

SCSI commands

FCP

Optical/Copper

Fibre Channel

SCSI commands

Partial FCP

SATA Copper

Serial Attached

SCSI (SAS)

SCSI commands

TCP/IP

Optical/Copper

iSCSI

Ethernet/other


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But other protocols areused by disk drives

Serial ATA (SATA) is used in lower-end drives Replaced parallel ATA, also called IDE SATA is quick, common, and cheap

Serial-Attached SCSI (SAS) is the next tier Replaced parallel SCSI as higher-end drive Shares common components with SATA but adds SCSI

command set (and command queueing)

Native Fibre Channel drives are still tops Have non-optical FC interconnect

Enterprise drives versus desktop drives Enterprise are more sturdy and pass more rigorous tests Spinning speed (RPM) has huge impact on performance


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Important Concept #4:RAID Combines Disks

A Redundant Array of Independent Disks (RAID) is

a combination of disk drives acting as one RAID can improve performance and reliability

RAID is as old as storage IBM patented the general concept in 1978 David Patterson, Garth Gibson, and Randy Katz defined

five idealized RAID levels in 1988 The I originally stood for inexpensive, but this proved

to be inaccurate once arrays were produced for sale!

Today there are literally dozens of differentimplementations of the RAID concept


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Common RAID Levels

RAID 0 Stripe

Poor reliability no dataprotection and double thechance of failure!

No wasted space

Fast reads and writes 2x!

RAID 1 Mirror

Good reliability

50% overhead for dataprotection

50% wasted space

2x fast reads but slowerwrites


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Common RAID Levels

RAID 4 Dedicated parity Good data protection

Less wasted space (N-1)

Nx faster reads but slowerwrites

Parity across blocks means

lots of recalculation if theyrenot written at the same time

RAID 5 Striped parity Good data protection

Less wasted space (N-1)

Nx faster reads but slowerwrites

Parity for each block means

they can easily be writtenindividually

P

PP

P

P

PP

P


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RAID Mashups

It is common to stack RAID levels as RAID X+Ywhere X is laid over top of Y

RAID 0+1 (or RAID 01) is mirrored stripes

RAID 1+0 (or RAID 10) is striped mirrors

RAID 5+0 (or RAID 50) is striped RAID 5

RAID 6 or RAID DP has two parity slots either aduplicate or an alternate calculation

RAID E mixes a hot spare disk into the striping

Some vendors use RAID on a region of a diskinstead of a whole disk drive


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Grid array

Important Concept #5:There are Three Kinds of Storage Array

Monolithic arrays are large cabinets withmany disk slots, controllers, and I/O paths IBM, EMC, and HDS started with the mainframe

Modular arrays use a 1- or 2-controllerhead and generic disk shelves that canbe added as needed 3Com was followed by NetApp, CLARiiON, etc Clustered heads and SAN storage can be used

Grid arrays have small nodes with a fewdrives that team up in flexible clusters forperformance and reliability Upstart CAS and iSCSI arrays were first to use

this concept

Monolithic array

Modular array


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Choices Abound forNetworked Enterprise Storage

No matter if youre looking for SAN, NAS, iSCSI, or

CAS there are lots of options There are monolithic, modular, and grid devices that

support most protocols

Every type of equipment and protocol couldsupport every type of application Databases can run great on NAS or RAID 5

You can build a cheap SAN with Fibre Channel or iSCSI NAS filers can make great archiving targets Workstations can share SAN storage CAS can be accessed with NFS or CIFS You can put tier-3 bulk storage on an enterprise array Modular arrays can outrun their big brothers


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Mixing Up the Right SAN

The best choice is the one that makes the most

sense in yourenvironment Select the right tool for the job instead of using a

wrench as a hammer Just because something canwork doesnt make it a good

idea Always pick the simplest and most straightforward solution

Look for the best fit for your budget and scale If you only have a few terabytes, buy just one networked

array that will work for most of your applications

Match your chosen technologies with the platformsand applications you have


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Architecture Example:Small Web Company

A small but growing business focused on a web-

based product Wants stability, flexibility, scalability, low cost, and DR All Windows, mostly file but with some block storage

Selected a modular NAS/iSCSI array NAS replaced all current Windows file servers

iSCSI replaced internal storage for email and database Picked a midrange device with lots of growth potential Used SATA drives with RAID 6 for reliability and good

enough performance Built-in snapshots and replication of both file and block

data from a single interface


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Architecture Example:Large Financial Company

A household name in the world of finance Wanted to implement tiered storage to save money Hundreds of TB, mixed Windows, UNIX, and mainframe

Selected a modular FC SAN device Sufficient staff and money to bring in a new storage

platform Spent time and money on data classification to move less

critical apps off Tier 1 Decided to consolidate Windows systems with

virtualization and blades rather than use iSCSI Deferred all enterprise storage purchases for two years Kept all mainframe data on Tier 1 enterprise storage for

now


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Closing Thoughts

Bring in the storage that is right for you Dont let rules of thumb and bogus best practices

prejudice your choice

All storage devices work pretty well these days -but none are perfect Dont try to do anything exotic with basic devices Use the right tool for the job

Make the vendors prove it works Talk to references who are doing what you want to do Create a proof of concept before buying

Remember that its not all about the technology even the best storage cant fill an uncertain need!


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Questions?

Audience Q&A: 10-15 minutes

Contact me at [email protected]

Come talk to me after the session or at lunch

I'll be available at the Ask-the-Expert booth todayand tomorrow from 5 PM to 6 PM
mailto:[email protected]:[email protected]:[email protected]


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For More Information

Contact me: Stephen Foskett [email protected]

Visit SearchStorage.com and read Storagemagazine

Get SNIAs "Network Storage Terms andAcronyms" book

Ask others here at the show or at user groups Storage Networking User Group (SNUG)

http://storagenetworking.org

Association of Storage Networking Professionals (ASNP) http://asnp.org

Ask the vendors (really!)
mailto:[email protected]://storagenetworking.org/http://asnp.org/http://asnp.org/http://storagenetworking.org/mailto:[email protected]

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