Storage Technology and Management W.lilakiatsakun

Storage Technology and Storage Technology and ManagementManagement

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Storage TechnologyStorage Technology

• JBOD (Just Bunch Of Disk)JBOD (Just Bunch Of Disk)

• RAID (Redundant arrays of RAID (Redundant arrays of inexpensive disks)inexpensive disks)

• SSA (Serial Storage Architecture)SSA (Serial Storage Architecture)

JBOD (Just Bunch Of Disk) JBOD (Just Bunch Of Disk) (1)(1)

JBOD (Just Bunch Of Disk) JBOD (Just Bunch Of Disk) (2)(2)• JBOD can be used as individual disks or any JBOD can be used as individual disks or any

RAID configuration RAID configuration or Concatenation or Concatenation (SPAN)(SPAN) dd epending on the Host Bus Adapter epending on the Host Bus Adapter

• ConcatenationConcatenation or Spanning of disks is a p or Spanning of disks is a p opular method for combining multiple phy opular method for combining multiple phy

sical disk drives into a single virtual disk. sical disk drives into a single virtual disk.– It provides no data redundancy. It provides no data redundancy.– DD isks are merely concatenated together so the isks are merely concatenated together so the

y appear to be a single large disk. y appear to be a single large disk.

JBOD (Just Bunch Of Disk) JBOD (Just Bunch Of Disk) (3)(3)

• For example, JBOD (Just a Bunch Of Di For example, JBOD (Just a Bunch Of Di sks) could combine sks) could combine33 GB, GB, 1515 GB, GB, 5.55.5 G G

B, and B, and 1212 GB drives into a logical driv GB drives into a logical driv e at e at 35.535.5 GB, which is often more usef GB, which is often more usef ul than the individual drives separatel ul than the individual drives separatel

y.y.

Redundant arrays of Redundant arrays of inexpensive disks (RAID)inexpensive disks (RAID)

• The organization distributes the dat The organization distributes the dat a across multiple smaller disks, off a across multiple smaller disks, off

ering protection from a crash that c ering protection from a crash that c ould wipe out all data on a single, sh ould wipe out all data on a single, sh ared disk. ared disk.

•Benefits are depended on level of Benefits are depended on level of RAID RAID

RAID0 (RAID0 (stripe setstripe set or or striped striped volumevolume) )

• RAID Level RAID Level 0 splits data evenly 0 splits data evenly across two or more disks across two or more disks (striped) with no parity (striped) with no parity information for redundancy. information for redundancy.

• It is important to note that It is important to note that RAID 0 provides zero data RAID 0 provides zero data redundancyredundancy. .

• RAID 0 is normally used RAID 0 is normally used to to increase performanceincrease performance

• A RAID A RAID 0 0 can be created with dis can be created with dis ks of differing sizes, but the stor ks of differing sizes, but the stor

age space added to the array b age space added to the array b y each disk is limited to the size y each disk is limited to the size of the smallest disk of the smallest disk

RAID0 – Summary (1)RAID0 – Summary (1)

• RAID RAID00 uses a very simple design and i uses a very simple design and i s easy to implement with a s easy to implement with a HUGE perfo HUGE perfo

rmance advantage rmance advantage . .• I/O performance is greatly improved by I/O performance is greatly improved by

spreading the I/O load across many ch spreading the I/O load across many ch annels and drives while the best perfor annels and drives while the best perfor mance is achieved mance is achieved when data is stripe when data is stripe

d across multiple controllers with only d across multiple controllers with only one drive per controller one drive per controller . .


• No parity calculation overhead is involv No parity calculation overhead is involveded

• Not a "True" RAID because it is NOT faul Not a "True" RAID because it is NOT faul- t tolerant.- t tolerant.

• The failure of just one drive will result in The failure of just one drive will result in all data in an array being lost. all data in an array being lost.

RAID1 RAID1 ((mirrormirrorringring))

• A A RAID RAID 1 1 creates an exact c creates an exact c opy of a set of data on two o opy of a set of data on two o

r more disks. r more disks.• This is useful when read per This is useful when read per

formance or reliability are formance or reliability are more important than data st more important than data st orage capacity. orage capacity.

• Such an array can only be a Such an array can only be a s big as the smallest memb s big as the smallest memb er disk. er disk.

• A classic RAID A classic RAID11 mirrored pa mirrored pa ir contains two disks which i ir contains two disks which i

ncreases reliability ncreases reliability


• RAID Level RAID Level11 requires a requires a minimum of minimum of22 drives drives to implement. to implement.

• 100100 redundancy of data means no rebuild is redundancy of data means no rebuild is necessary in case of a disk failure, just a cop necessary in case of a disk failure, just a cop

y to the replacement disk. y to the replacement disk.• Transfer rate per block is equal to that of a si Transfer rate per block is equal to that of a si

ngle disk. ngle disk.• Simplest RAID storage subsystem design. Simplest RAID storage subsystem design.


• Highest disk overhead Highest disk overhead - of all RAID types ineff - of all RAID types ineff icient due to the duplication of Write tasks. icient due to the duplication of Write tasks.

• Typically the RAID function is done by system Typically the RAID function is done by system software, loading the CPU/Server and possibly software, loading the CPU/Server and possibly degrading throughput at high activity levels. degrading throughput at high activity levels.

• Hardware implementation is strongly recomm Hardware implementation is strongly recommendedended..– May not support hot swap of failed disk when imple May not support hot swap of failed disk when imple

mented in "software". mented in "software".

RAID 0 +1 (RAID 0 +1 ( A Mirror of Stripe A Mirror of Stripess))

• RAID Level RAID Level 0+10+1 is i is i mplemented as a m mplemented as a m

irrored array whose irrored array whose segments are RAID segments are RAID

00 arrays. arrays.

• RAID Level RAID Level 0+10+1 req req uires a minimum of uires a minimum of

44 drives to impleme drives to implementnt

RAID 10 (A Stripe of Mirrors)RAID 10 (A Stripe of Mirrors)

• RAID RAID 1010 is impleme is impleme nted as a striped ar nted as a striped ar

ray whose segment ray whose segment s are RAID s are RAID11 arrays. arrays.

• RAID Level RAID Level 1010 requ requ ires a minimum of ires a minimum of44

drives to implemen drives to implement.t.

RAID3 RAID3 (( Parallel access with a d Parallel access with a d edicated parity disk edicated parity disk))

• RAID Level RAID Level33 uses uses - byte level- byte level striping with a dedicated pa striping with a dedicated pa

rity disk. rity disk.

• This comes about because a This comes about because a ny single block of data will ny single block of data will bb

e spread across all member e spread across all member s of the set and will reside in s of the set and will reside in

the same location. the same location.

• So, any I/O operation requir So, any I/O operation requir es activity on every disk. es activity on every disk.

RAID3 – Summary RAID3 – Summary

• Level Level33 only requires one dedicated disk in t only requires one dedicated disk in t he array to hold parity information. he array to hold parity information.

• The server's data is then striped across the r The server's data is then striped across the r emaining drives, usually one byte at a time. emaining drives, usually one byte at a time.

• The parity drive then keeps track of all the in The parity drive then keeps track of all the in fo on the striped drive(s) and uses it to resto fo on the striped drive(s) and uses it to resto re info if the drive should fail. re info if the drive should fail.

• Because of the parity information that is stor Because of the parity information that is stor ed and because Write operations take place ed and because Write operations take place on a byte level, Read/Write operations often on a byte level, Read/Write operations often

take longer than other RAID configurations. take longer than other RAID configurations.

RAID5 RAID5 (( Independent access wit Independent access wit h distributed parit h distributed parity)y)

• A A RAID RAID55 uses uses - block level- block level strstr iping with parity data distribu iping with parity data distribu

ted across all member disks. ted across all member disks.• A minimum of A minimum of33 disks is gene disks is gene

rally required for a complete rally required for a complete RAID RAID55 configuration. configuration.

• In the example, a read reque In the example, a read reque st for block "A st for block "A11 " would be ser " would be ser

viced by disk viced by disk00..• A simultaneous read request A simultaneous read request

for block B for block B11 would have to w would have to w ait, but a read request for B ait, but a read request for B22

could be serviced concurrent could be serviced concurrent ly by disk ly by disk 11

RAID 5 – Summary RAID 5 – Summary

• Level Level55 also relies on parity information to provide also relies on parity information to provide redundancy and fault tolerance using independent redundancy and fault tolerance using independent

data disks with distributed parity blocks. data disks with distributed parity blocks.• Each entire data block is written onto a data disk; Each entire data block is written onto a data disk;

parity for blocks in the same rank is generated on parity for blocks in the same rank is generated on Writes, recorded in a distributed location and chec Writes, recorded in a distributed location and chec

ked on Reads. Compared to RAID ked on Reads. Compared to RAID33 , RAID , RAID55 uses st uses st riping to spread parity information across multiple riping to spread parity information across multiple drives. drives.

• Requirements:Requirements: RAID Level RAID Level55 requires a minimum requires a minimum of of33 drives to implement. drives to implement.

SSA (Serial Storage SSA (Serial Storage Architecture) (1)Architecture) (1)

• Serial Storage Architecture (SSA) defines a h Serial Storage Architecture (SSA) defines a h- igh performance serial link for the attachme- igh performance serial link for the attachme

nt of input/output devices. nt of input/output devices.– It has been optimized for storage applications suc It has been optimized for storage applications suc

h as hard disk drives, host adapter cards, and arr h as hard disk drives, host adapter cards, and arr ay controllers. ay controllers.

• SSA has many advantages over existing par SSA has many advantages over existing par allel interfaces such as the Small Computer allel interfaces such as the Small Computer

Systems Interface (SCSI Systems Interface (SCSI-2-2 ). ).– It uses compact cables and connectors, and it ha It uses compact cables and connectors, and it ha

s better performance, connectivity, and reliability s better performance, connectivity, and reliability . .


• Disk Subsystem provide a peak data rate o Disk Subsystem provide a peak data rate o f f 2020 MB/s in each direction. MB/s in each direction.

• However, a typical loop configuration with However, a typical loop configuration with one host adapter can provide a total sustai one host adapter can provide a total sustai ned bandwidth of up to ned bandwidth of up to 8080 MB/s, and higher MB/s, and higher

speeds are becoming available. speeds are becoming available.

• The physical medium is usually a copper ca The physical medium is usually a copper ca ble up to ble up to 2020 meters long, but fiber optics ca meters long, but fiber optics ca

n also be used for longer distances. n also be used for longer distances.



• Architecture overview Architecture overview• SSA is defined in three layers: SSA is defined in three layers:• -SSA PH-SSA PH11 defines the electrical specification defines the electrical specification

s, cables, and connectors. s, cables, and connectors.• -SSA TL-SSA TL11 - is a general purpose transport lay - is a general purpose transport lay

er. It defines the transmission protocol, con er. It defines the transmission protocol, con figuration, and error recovery. figuration, and error recovery.

• -SSA S-SSA S22PP -is a mapping of the SCSI -is a mapping of the SCSI 22 queuin queuin g model, command set, status, and sense b g model, command set, status, and sense b

ytes. ytes.

Storage ModelStorage Model

Storage Area NetworkStorage Area Network

• AA - SAN is a specialized, high speed network - SAN is a specialized, high speed network attaching servers and storage devices attaching servers and storage devices

• It is sometimes referred to as It is sometimes referred to as “the network “the network behind the servers.” behind the servers.”

• AA SAN introduces the flexibility of networki SAN introduces the flexibility of networki ng to enable one server or many heteroge ng to enable one server or many heteroge

neous servers to share a common storage neous servers to share a common storage utility, which may comprise many storage utility, which may comprise many storage

devices, including disk, tape, and optical st devices, including disk, tape, and optical storage.orage.

SAN ComponentSAN Component

• SAN Connectivity SAN Connectivity – the connectivity of storage and server the connectivity of storage and server

components typically using components typically using Fibre Channel Fibre Channel (FC).(FC).

• SAN StorageSAN Storage– TAPE /RAID /JBOD (Just Bunch of Disk) /SSA TAPE /RAID /JBOD (Just Bunch of Disk) /SSA

(Serial Storage Architecture)(Serial Storage Architecture)

• SAN ServerSAN Server– Windows /Unix /Linux and etcWindows /Unix /Linux and etc

Switched FabricSwitched Fabric

• AA n infrastructure specially designed to ha n infrastructure specially designed to ha ndle storage communications called a fabr ndle storage communications called a fabr

ic. ic.• A typical Fibre Channel SAN fabric is made A typical Fibre Channel SAN fabric is made

up of a number of Fibre Channel switches. up of a number of Fibre Channel switches.• Today, all major SAN equipment vendors a Today, all major SAN equipment vendors a

lso offer some form of Fibre Channel routi lso offer some form of Fibre Channel routi ng solution, and these bring substantial sc ng solution, and these bring substantial sc

alability benefits to the SAN architecture b alability benefits to the SAN architecture b y allowing data to cross between different y allowing data to cross between different

fabrics without merging them. fabrics without merging them.

Fiber Channel protocol (1)Fiber Channel protocol (1)

• FCFC00 The physical layer The physical layer , which includes cabl , which includes cabl es, fiber optics, connectors, pinouts etc. es, fiber optics, connectors, pinouts etc.

• FC1FC1 The data link layer The data link layer , which implements t , which implements thehe 8b/10b 8b/10b encoding and decoding of signals. encoding and decoding of signals.

• FCFC22 The network layer The network layer , defined by the , defined by the- - 2FC PI- - 2FC PI standard, consists of the core of Fibre standard, consists of the core of Fibre

Channel, and defines the main protocols. Channel, and defines the main protocols.

Fiber Channel protocol (2)Fiber Channel protocol (2)

• FCFC33 The common services layer The common services layer , a t , a t hin layer that could eventually imple hin layer that could eventually imple

ment functions like encryption or RAI ment functions like encryption or RAI D. D.

• FCFC44 The Protocol Mapping layer The Protocol Mapping layer . Lay . Lay er in which other protocols, such as S er in which other protocols, such as S

CSI, are encapsulated into an informa CSI, are encapsulated into an informa tion unit for delivery to tion unit for delivery to FC2.FC2.

Storage ManagementStorage Management

• Monitoring disk useMonitoring disk use– Disk monitor agent scans the server volumes Disk monitor agent scans the server volumes

to collect disk use informationto collect disk use information

• Hierarchical storage managementHierarchical storage management– Files will be archived according to certain Files will be archived according to certain

criteria criteria

• Prevention against Data Loss Prevention against Data Loss – To protect and recovery from lossTo protect and recovery from loss

• Outsourcing storage managementOutsourcing storage management

Monitoring disk useMonitoring disk use

• One or more the following categories of One or more the following categories of information can be collectedinformation can be collected– VolumesVolumes:(Disk) total space : used /available:(Disk) total space : used /available– DirectoriesDirectories: what are there : what are there – Directory and File ownersDirectory and File owners: who create / who use : who create / who use

/when create /when create

Hierarchical storage Hierarchical storage managementmanagement

• When disk space becomes exhausted , data When disk space becomes exhausted , data files need to be backup (as archived file or back files need to be backup (as archived file or back up tape)up tape)– Software tools (Back up tools)Software tools (Back up tools)

• When a file system reaches a predefined When a file system reaches a predefined threshold of X percent fullthreshold of X percent full– automated procedureautomated procedure are initiated that determine are initiated that determine

which files are eligible for archive and are currently which files are eligible for archive and are currently backed upbacked up

– The file catalog is then updatedThe file catalog is then updated to indicate that files to indicate that files have been archived and deletes them from the disk have been archived and deletes them from the disk file system file system

Prevention against data loss Prevention against data loss (1/2)(1/2)

• Data perspectiveData perspective– - Backups sent off site in regular intervals - Backups sent off site in regular intervals– Use a Remote backup facility if possible to mi Use a Remote backup facility if possible to mi

nimize data loss nimize data loss– Storage Area Networks (SANs) over multiple Storage Area Networks (SANs) over multiple

sites make data immediately available witho sites make data immediately available witho ut the need to recover or synchronize it ut the need to recover or synchronize it

Prevention against data loss Prevention against data loss (2/2)(2/2)

• Facility perspectiveFacility perspective– Surge Protectors — to minimize the effect of Surge Protectors — to minimize the effect of

power surges on delicate electronic equipme power surges on delicate electronic equipme nt nt

– Uninterruptible Power Supply (UPS) and/or B Uninterruptible Power Supply (UPS) and/or B ackup Generator ackup Generator

– Fire Preventions — more alarms, accessible e Fire Preventions — more alarms, accessible e xtinguishers xtinguishers

– - Anti virus software and other security measu- Anti virus software and other security measu res res

Techniques to prevent data Techniques to prevent data lossloss• MirroringMirroring

– Disk mirroring : Redundant arrays of inexpensive Disk mirroring : Redundant arrays of inexpensive disks 1 (RAID1)disks 1 (RAID1)

– Server mirroring: web / ftp /emailServer mirroring: web / ftp /email

• On-site data storageOn-site data storage– Back up - Tape / optical disk Back up - Tape / optical disk

• Off-site data storage (backup-site)Off-site data storage (backup-site)– Cold sitesCold sites– Warm sitesWarm sites– Hot siteHot site

Mirroring Mirroring

• Mirroring can occur locally or remotely. Mirroring can occur locally or remotely.– Locally means that a server has a second hard driv Locally means that a server has a second hard driv

e that stores data. e that stores data.– A remote mirror means that a remote server contai A remote mirror means that a remote server contai

ns an exact duplicate of the data. ns an exact duplicate of the data.

• Data is written to the original drive when a writ Data is written to the original drive when a writ e request is issued e request is issued andand then copied to the mirr then copied to the mirr

ored drive, providing a mirror image of the pri ored drive, providing a mirror image of the pri mary drive. mary drive.

Disk mirroring (RAID1)Disk mirroring (RAID1)

• TT he replication of logical he replication of logical disk volumes onto separ disk volumes onto separ

ate physical hard disks in ate physical hard disks in real time to ensure conti real time to ensure conti

nuous availability, curre nuous availability, curre ncy and accuracy. ncy and accuracy.

• A A mirrored volume mirrored volume is a is a complete logical represe complete logical represe

ntation of separate volu ntation of separate volu me copies me copies

Server mirroringServer mirroring

• Mirror sites are most commonly usedMirror sites are most commonly used to provide to provide multiple sources of the same information, and are of multiple sources of the same information, and are of particular value as a way of providing reliable access particular value as a way of providing reliable access to large downloads. to large downloads.

• Web serverWeb server– To preserve a website or page, especially when it is closed or To preserve a website or page, especially when it is closed or

is about to be closedis about to be closed– Load balancingLoad balancing

• Email serverEmail server– To protect loss of email informationTo protect loss of email information

• ftp serverftp server– To allow faster downloads for users at a specific geographical To allow faster downloads for users at a specific geographical

locationlocation– Load balancingLoad balancing

Back up site Back up site

• A A backup site backup site is a location where a business c is a location where a business c an easily relocate following a disaster, such as an easily relocate following a disaster, such as

fire, flood, or terrorist threat. This is an integral fire, flood, or terrorist threat. This is an integral part of the disaster recovery plan of a business part of the disaster recovery plan of a business

..

• A backup site can be another location operated A backup site can be another location operated by the business, or contracted via a company t by the business, or contracted via a company t hat specializes in disaster recovery services. hat specializes in disaster recovery services.

• In some cases, a business will have an agreem In some cases, a business will have an agreem ent with a second business to operate a joint di ent with a second business to operate a joint di

saster recovery facility. saster recovery facility.

Cold Sites Cold Sites

• A cold site is the most inexpensive type of back A cold site is the most inexpensive type of back up site for a business to operate. up site for a business to operate.

• It provides office spaces to operateIt provides office spaces to operate• It does not include backed up copies of data an It does not include backed up copies of data an

d information from the original location of the b d information from the original location of the b usiness, nor does it include hardware already s usiness, nor does it include hardware already s

et up. et up.• The lack of hardware contributes to the minima The lack of hardware contributes to the minima

l startup costs of the cold site, but requires addi l startup costs of the cold site, but requires addi tional time following the disaster to have the op tional time following the disaster to have the op

eration running at a capacity close to that prior eration running at a capacity close to that prior to the disaster. to the disaster.

Warm Sites Warm Sites

• A warm site is a location where the busin A warm site is a location where the busin ess can relocate to after the disaster tha ess can relocate to after the disaster tha

t is already stocked with computer hard t is already stocked with computer hard ware similar to that of the original site, b ware similar to that of the original site, b

ut does not contain backed up copies of ut does not contain backed up copies of data and information. data and information.

Hot Sites Hot Sites

• A hot site is a duplicate of the original site of th A hot site is a duplicate of the original site of th e business, with full computer systems as well e business, with full computer systems as well - as near complete backups of user data. - as near complete backups of user data.

• Ideally, a hot site will be up and running within Ideally, a hot site will be up and running within a matter of hours. This type of backup site is th a matter of hours. This type of backup site is th e most expensive to operate. e most expensive to operate.

• Hot sites are popular with stock exchanges and Hot sites are popular with stock exchanges and other financial institutions who may need to ev other financial institutions who may need to ev

acuate due to potential bomb threats and must acuate due to potential bomb threats and must resume normal operations as soon as possible. resume normal operations as soon as possible.

How to choose (1)How to choose (1)

• Choosing the type is mainly decided by a c Choosing the type is mainly decided by a c ompany's cost vs. benefit strategy. ompany's cost vs. benefit strategy.

• Hot sites are traditionally more expensive t Hot sites are traditionally more expensive t han cold sites since much of the equipmen han cold sites since much of the equipmen

t the company needs has already been pur t the company needs has already been pur chased and thus the operational costs are chased and thus the operational costs are higher. higher.

• However if the same company loses a subs However if the same company loses a subs tantial amount of revenue for each day the tantial amount of revenue for each day the

y are inactive then it may be worth the cos y are inactive then it may be worth the cost.t.

How to choose (2)How to choose (2)

• --The advantages of a cold site are simple c --The advantages of a cold site are simple c ost. It requires much fewer resources to op ost. It requires much fewer resources to op

erate a cold site because no equipment ha erate a cold site because no equipment ha s been bought prior to the disaster. s been bought prior to the disaster.

• The downside with a cold site is the potenti The downside with a cold site is the potenti al cost that must be incurred in order to m al cost that must be incurred in order to m

ake the cold site effective. ake the cold site effective.• The costs of purchasing equipment on very The costs of purchasing equipment on very

short notice may be higher and the disaste short notice may be higher and the disaste r may make the equipment difficult to obta r may make the equipment difficult to obta

in.in.

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Storage Technology and Management W.lilakiatsakun