Storage Area Networks1

7/29/2019 Storage Area Networks1

1/7

A Paper Presentation on----

STORAGE AREA NETWORKS

PRESENTED BY:

G V SAI CHAND R LAKSHMI BHAVANI

IV B.TECH IV B.TECHEMAIL: [email protected]

DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

CHEBROLU ENGINEERING COLLEGE

CHEBROLU- 522002


2/7

Abstract:

Storage Area Networks (SANs) have the virtues of high scalability, high availability and high performance. On the other hand,their storage virtualization systems are not compatible withmulti-operating systems, and it is hard for the virtualization storage management system tomanage multi-type storage. This paper proposes a new virtualization storage management modelfor SANs.

1. Introduction

Storage Area Networks (SANs)use a net-oriented storage structure,which enables the separation of data

processing and data storage. SANs havethe virtue of high availability andscalability, high I/O performance, anddata sharing. SANs employ backup,remote mirroring, and virtualizationfunctions, which has made them more

popular. The storage virtualizationmanagement system can manage variousstorage systems which still provide oneuniform interface for users. Various

storage systems, such as XIOtech[3]

,IBM [4] , EMC [5] , all have their ownvirtualization management systems,which add extra complexity anddifficultly.

What is a storage area network

The Storage Networking IndustryAssociation (SNIA) defines the storage areanetwork (SAN )as a network whose primary purpose is thetransfer of data between computer systemsand storage elements. A SAN consists of acommunication infrastructure, which

provides physical connections. It alsoincludes a management layer, whichorganizes the connections, storage elements,and computer systems so that data transfer issecure and robust.

In simple terms, a SAN is a specialized, high-speed network that attaches servers andstorage devices. For this reason, it issometimes referred to as the network behind the servers. A SAN allows an any-to-any connection across the network, by usinginterconnect elements such as switches anddirectors.


3/7

Using a SAN can potentially offer thefollowing benefits:- Improvements to application availability:Storage is independent of applications andaccessible through multiple data paths for

better reliability, availability, andserviceability.- Higher application performance: Storage

processing is offloaded from servers andmoved onto a separate network.-Centralized and consolidated storage: Simpler management, scalability, flexibility, andavailability.- Data transfer and vaulting to remote sites:Remote copy of data that is enabled for disaster

protection and against malicious attacks.-Simplified centralized management: Singleimage of storage media simplifiesmanagement.

Storage area network storage

The storage area network (SAN) liberates thestorage device so it is not on a particular server

bus, and attaches it directly to the network. Inother words, storage is externalized and can befunctionally distributed across the

organization. The SAN also enables thecentralization of storage devices and the clustering of servers.

Different technologies

Multiple technology can be used when building a SAN; traditionally thedominant technology is Fiber Channel,

but IP based solutions are also quite popular for specific applications

The concept of SAN is alsoindependent from the devices that areattached to it. Can be disks, tapes,RAIDs, file servers, or other Storage.

Disk systemsIn brief a disk system is a device in which a

number of physical storage disks sitside-by-side. By being contained within asingle box, a disk system usually hasa central control unit that manages all the I/O,simplifying the integration of thesystem with other devices, such as other disk systems or servers.Depending on the intelligence with whichthis central control unit is able tomanage the individual disks, a disk system can

be a JBOD or a RAID.Just A Bunch Of Disks (JBOD)

In this case, the disk system appears as a set of individualstorage devices to the device they are attachedto. Thecentral control unit provides only basicfunctionality for writing and reading data from the disks.16Introduction to Storage Area NetworksRedundant Array of Independent Disks(RAID)In this case, the central control unit providesadditionalfunctionality that makes it possible to utilizethe individualdisks in such a way to achieve higher fault-toleranceand/or performance. The disks themselvesappear as asingle storage unit to the devices to which theyareconnected.Depending on the specific functionalityoffered by a particular disk system, it is

possible to make it behave as a RAID and/or aJBOD; the decision as to which


4/7

type of disk system is more suitable for a SANimplementation strongly dependson the performance and availabilityrequirements for this particular SAN.

A group of hard disks is called a disk array

RAID combines a disk array into asingle virtual device

called RAID drive Provide fault tolerance for shared data

and applications Different implementations: Level 0-5 Characteristics:

Storage Capacity Speed: Fast Read and/or Fast

Write Resilience in the face of

device failureRAID Types RAID 0

Stripe with no parity (see nextslide for figure)

RAID 1 Mirror two or more disks

RAID 0+1 (or 1+0) Stripe and Mirrors

RAID 3 Synchronous, Subdivided

Block Access; Dedicated

Parity Drive RAID 5

Like RAID 4, but paritystriped across multiple drives

Tape systemsTape systems, in much the same way as disk systems do, are devices thatcomprise all the necessary apparatus tomanage the use of tapes for storage

purposes. In this case, however, the serialnature of a tape makes it impossiblefor them to be treated in parallel, as RAIDdevices are leading to a somewhatsimpler architecture to manage and use.There are basically three types of systems:drives, autoloaders and libraries, thatare described as follows.Tape drivesAs with disk drives, tape drives are the means

by which tapes can be connectedto other devices; they provide the physical andlogical structure for reading from,and writing to tapes.Tape autoloaders

Tape autoloaders are autonomous tape drivescapable of managing tapes and

performing automatic back-up operations.They are usually connected tohigh-throughput devices that require constantdata back-up.Tape librariesTape libraries are devices capable of managingmultiple tapes simultaneouslyand, as such, can be viewed as a set of independent tape drives or autoloaders.They are usually deployed in systems thatrequire massive storage capacity, or that need some kind of data separation thatwould result in multiple single-tapesystems. As a tape is not a random-accessmedia, tape libraries cannot provide

parallel access to multiple tapes as a way toimprove performance, but they can provide redundancy as a way to improve dataavailability and fault-tolerance.

Architectures:

Direct Attached Storage (DAS)

Direct attached storage is the simplest andmost commonly used storage model found inmost

standalone PCs, workstations and servers. Atypical DAS configuration consists of acomputer that is directly connected to one or several hard disk drives (HDDs) or disk arrays.

DAS is a widely deployed technology inenterprise networks. It is easy to understand,acquire andinstall, and is low cost. It is well suited to the

purpose of attaching data storage resources toacomputer or a server when capacity,administration, backup, high-availability, high

performanceare not key requirements. For home PC andsmall enterprise network applications, DAS isstillthe dominant choice, as the low-endrequirements for growth in capacity,

performance andreliability can be easily addressed by theadvancements in HDD and bus technologies.


5/7

Network Attached Storage (NAS)After seeing the consequences of bindingstorage to individual computers in the DASmodel, the

benefits of sharing storage resources over thenetwork become obvious. NAS and SAN aretwoways of sharing storage over the network.

NAS is generally referred to as storage that isdirectlyattached to a computer network (LAN)through network file system protocols such as

NFS andCIFS.

The benefit that comes with the higher layer abstraction in NAS is ease-of-use. Manyoperatingsystems, such as UNIX and LINUX, haveembedded support for NAS protocols such as

NFS.Later versions of Windows OS have alsointroduced support for the CIFS protocol.Setting up a

NAS system, then, involves connecting the NAS storage system to the enterprise LAN(e.g.Ethernet) and configuring the OS on theworkstations and servers to access the NASfiler. Themany benefits of shared storage can then be

easily realized in a familiar LAN environmentwithout introducing a new network infrastructure or new switching devices.

Storage Area Network (SAN)

SAN provides block-orient I/O between thecomputer systems and the target disk systems.TheSAN may use Fibre Channel or Ethernet

(iSCSI) to provide connectivity between hostsandstorage. In either case, the storage is physicallydecoupled from the hosts. The SAN is often

built on a dedicated network fabric that isseparated from the LAN network to ensure thelatency-sensitive block I/OSAN traffic does not interfere with the trafficon the LAN network. This examples shows andedicated SAN network connecting multipleapplication servers, database servers, NASfilers onone side, and a number of disk systems andtape drive system on the other. The servers andthestorage devices are connected together by theSAN as peers.


6/7

Storage Area Network ComponentsAs previously discussed, the primarytechnology used in storage area networkstoday is Fibre Channel. This section provides a

basic overview of the components in a fibrechannel storage fabric as well as differenttopologies and configurations open toWindows deployments.

Fibre Channel TopologiesFundamentally, fibre channel defines threeconfigurations:

Point-to-point

Fibre Channel Arbitrated Loop (FC-AL)

Switched Fibre Channel Fabrics (FC-SW).

Although the term fibre channel impliessome form of fibre optic technology, the fibrechannel specification allows for both fibreoptic interconnects as well as copper coaxialcables.

Point-to-PointPoint-to-point fibre channel is a simple way toconnect two (and only two) devices directlytogether, as shown in Figure 1 below. It is the

fibre channel equivalent of direct attachedstorage (DAS).

Figure 1: Point to point connection

From a cluster and storage infrastructure perspective, point-to-point is not a scalableenterprise configuration and we will notconsider it again in this document.

Arbitrated Loops

A fibre channel arbitrated loop is exactly whatit says; it is a set of hosts and devices that areconnected into a single loop, as shown inFigure 2 below. It is a cost-effective way toconnect up to 126 devices and hosts into asingle network.

Figure 2: Fibre Channel arbitrated loop

Devices on the loop share the media; eachdevice is connected in series to the next devicein the loop and so on around the loop. Any

packet traveling from one device to another must pass through all intermediate devices. Inthe example shown, for host A tocommunicate with device D, all traffic

between the devices must flow through theadapters on host B and device C. The devices

in the loop do not need to look at the packet;they will simply pass it through. This is all


7/7

done at the physical layer by the fibre channelinterface card itself; it does not require

processing on the host or the device. This isvery analogous to the way a token-ringtopology operates.

Fibre Channel Switched Fabric

In a switched fibre channel fabric, devices areconnected in a many-to-many topology using

fibre channel switches , as shown in Figure 4below. When a host or device communicateswith another host or device, the source andtarget setup a point-to-point connection (justlike a virtual circuit) between them andcommunicate directly with each other. The

fabric itself routes data from the source to thetarget. In a fibre channel switched fabric, themedia is not shared. Any device cancommunicate with any other device(assuming it is not busy) and communicationoccurs at full bus speed (1Gbit/Sec or2Gbit/sec today depending on technology)irrespective of other devices and hostscommunicating.

Conclusion

SAN is a data centric network.It is deployedover networks and devices for data

management and enterprise growth wheredata security id of main concern. The storagenetworking has built a working area and willcome out with specifiations and standardrecommendations.

Reference

[1] B.Phillips, Have storage area networks

come of age? [J] IEEE Computer, vol.31,

no.7, 10-12, July 1998

[2] R. Khattar, et al., Introduction to

Storage Area Network: Redbooks Publications

(IBM) ,1999

[3] XIOTech Corp.,http://www.xiotec h.com/ ,

May2004.

[4]IBM Corp .http://www.redbooks.ibm.com/pu

bs/pdfs/redbo oks/sg245470.pdf , March 2003,

[5] EMC Corp. http://www.emc.com/products/storage_manag ement/controlcenter/pdf/H1140_cntrlctr_srm

_ plan_ds_ldv.pdf , May 2004.

Referenced websites:

1. IBM System Storage: Storage areanetworks

http://www-03.ibm.com/servers/storage/san/

2. Cisco

http://www.cisco.com 3. Brocade

http://www.brocade.com 4. QLogic

http://www.qlogic.com
http://www.xiotech.com/http://www.xiotech.com/http://www.redbooks.ibm.com/pubs/pdfs/redbohttp://www.redbooks.ibm.com/pubs/pdfs/redbohttp://www.redbooks.ibm.com/pubs/pdfs/redbohttp://www.emc.com/products/storage_managhttp://www.emc.com/products/storage_managhttp://www-03.ibm.com/servers/storage/san/http://www-03.ibm.com/servers/storage/san/http://www-03.ibm.com/servers/storage/san/http://www.cisco.com/http://www.cisco.com/http://www.brocade.com/http://www.brocade.com/http://www.qlogic.com/http://www.qlogic.com/http://www.qlogic.com/http://www.brocade.com/http://www.cisco.com/http://www-03.ibm.com/servers/storage/san/http://www-03.ibm.com/servers/storage/san/http://www.emc.com/products/storage_managhttp://www.redbooks.ibm.com/pubs/pdfs/redbohttp://www.redbooks.ibm.com/pubs/pdfs/redbohttp://www.xiotech.com/

Storage Area Networks1

Documents

Transcript of Storage Area Networks1