storages area networks

7/29/2019 Storages Area Networks

1/8

A Paper Presentation on----

STORAGE AREA NETWORKS

PRESENTED BY:

G V SAI CHAND R

LAKSHMI BHAVANI

IV B.TECH IV

B.TECH EMAIL:

[email protected]

DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING

CHEBROLU ENGINEERING COLLEGE

1


2/8

CHEBROLU- 522002

Abstract:

Storage Area Networks (SANs) have the virtues of high scalability, high availability and highperformance. On the other hand,their storage virtualization systems are not compatible with

multi-operating systems, and it is hard for the virtualization storage management system to

manage multi-type storage. This paperproposes a new virtualization storage management model

for SANs.

1. Introduction

Storage Area Networks (SANs)use a net-oriented storage structure,

which enables the separation of data

processing and data storage. SANs have

the virtue of high availability and

scalability, high I/O performance, and

data sharing. SANs employ backup,

remote mirroring, and virtualization

functions, which has made them more

popular. The storage virtualization

management system can manage various

storage systems which still provide one

uniform interface for users. Various

storage systems, such as XIOtech[3]

,

IBM[4]

, EMC[5]

, all have their own

virtualization management systems,

which add extra complexity and

difficultly.

What is a storage area network

The Storage Networking IndustryAssociation (SNIA) defines the storage area

network(SAN)

as a network whose primary purpose is the

transfer of data between computer systems

and storage elements. A SAN consists of a

communication infrastructure, which

provides physical connections. It also

includes a management layer, which

organizes the connections, storage elements,

and computer systems so that data transfer is

secure and robust.

In simple terms, a SAN is a specialized, high-

speed network that attaches servers and

storage devices. For this reason, it is

sometimes referred to as the network behind

the servers. A SAN allows an any-to-any

connection across the network, by using

interconnect elements such as switches and

directors.

2


3/8

Using a SAN can potentially offer the

following benefits:

- Improvements to application availability:

Storage is independent of applications and

accessible through multiple data paths for

better reliability, availability, and

serviceability.

- Higher application performance: Storage

processing is offloaded from servers and

moved onto a separate network.

-Centralized and consolidated storage: Simpler

management, scalability, flexibility, and

availability.

- Data transfer and vaulting to remote sites:

Remote copy of data that is enabled for

disasterprotection and against malicious attacks.

-Simplified centralized management: Single

image of storage media simplifies

management.

Storage area network storage

The storage area network (SAN) liberates the

storage device so it is not on a particular server

bus, and attaches it directly to the network. In

other words, storage is externalized and can be

functionally distributed across theorganization. The SAN also enables the

centralization of

storage devices and the clustering of servers.

Different technologies

Multiple technology can be used when

building a SAN; traditionally the

dominant technology is Fiber Channel,

but IP based solutions are also quite

popular for specific applications

The concept of SAN is also

independent from the devices that are

attached to it. Can be disks, tapes,

RAIDs, file servers, or otherStorage.

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

number of physical storage disks sit

side-by-side. By being contained within a

single box, a disk system usually has

a central control unit that manages all the I/O,

simplifying the integration of the

system with other devices, such as other disk

systems or servers.

Depending on the intelligence with which

this central control unit is able to

manage 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

individual

storage devices to the device they are attached

to. The

central control unit provides only basic

functionality for

writing and reading data from the disks.16

Introduction to Storage Area Networks

Redundant Array of Independent Disks

(RAID)

In this case, the central control unit providesadditional

functionality that makes it possible to utilize

the individual

disks in such a way to achieve higher fault-

tolerance

and/or performance. The disks themselves

appear as a

single storage unit to the devices to which they

are

connected.

Depending on the specific functionality

offered by a particular disk system, it is


4/8

possible to make it behave as a RAID and/or a

JBOD; the decision as to which

type of disk system is more suitable for a SAN

implementation strongly depends

on the performance and availability

requirements for this particular SAN.

A group of hard disks is called a disk

array

RAID combines a disk array into a

single 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 failure

RAID Types

RAID 0

Stripe with no parity (see next

slide for figure)

RAID 1

Mirror two or more disks

RAID 0+1 (or 1+0)

Stripe and Mirrors

RAID 3

Synchronous, SubdividedBlock Access; Dedicated

Parity Drive

RAID 5

Like RAID 4, but parity

striped across multiple drives

Tape systems

Tape systems, in much the same way as disk

systems do, are devices that

comprise all the necessary apparatus to

manage the use of tapes for storage

purposes. In this case, however, the serialnature of a tape makes it impossible

for them to be treated in parallel, as RAID

devices are leading to a somewhat

simpler architecture to manage and use.

There are basically three types of systems:

drives, autoloaders and libraries, that

are described as follows.

Tape drives

As with disk drives, tape drives are the means

by which tapes can be connected

to other devices; they provide the physical and

logical structure for reading from,

and writing to tapes.

Tape autoloaders

Tape autoloaders are autonomous tape drives

capable of managing tapes and

performing automatic back-up operations.

They are usually connected to

high-throughput devices that require constant

data back-up.

Tape libraries

Tape libraries are devices capable of managing

multiple tapes simultaneously

and, as such, can be viewed as a set of

independent tape drives or autoloaders.

They are usually deployed in systems that

require massive storage capacity, or

that need some kind of data separation that

would result in multiple single-tape

systems. As a tape is not a random-access

media, tape libraries cannot provideparallel access to multiple tapes as a way to

improve performance, but they can

provide redundancy as a way to improve data

availability and fault-tolerance.

Architectures:

Direct Attached Storage (DAS)

Direct attached storage is the simplest and

most commonly used storage model found in

moststandalone PCs, workstations and servers. A

typical DAS configuration consists of a

computer that is directly connected to one or

several hard disk drives (HDDs) or disk arrays.

DAS is a widely deployed technology in

enterprise networks. It is easy to understand,

acquire and

install, and is low cost. It is well suited to the

purpose of attaching data storage resources to

a

computer or a server when capacity,administration, backup, high-availability, high

performance

are not key requirements. For home PC and

small enterprise network applications, DAS is

still

the dominant choice, as the low-end

requirements for growth in capacity,

performance and

reliability can be easily addressed by the

advancements in HDD and bus technologies.


5/8

Network Attached Storage (NAS)

After seeing the consequences of binding

storage to individual computers in the DAS

model, the

benefits of sharing storage resources over the

network become obvious. NAS and SAN are

two

ways of sharing storage over the network.

NAS is generally referred to as storage that isdirectly

attached to a computer network (LAN)

through network file system protocols such as

NFS and

CIFS.

The benefit that comes with the higher layer

abstraction in NAS is ease-of-use. Many

operating

systems, such as UNIX and LINUX, have

embedded support for NAS protocols such as

NFS.

Later versions of Windows OS have also

introduced 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 the

workstations and servers to access the NAS

filer. The

many 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 the

computer systems and the target disk systems.

The

SAN may use Fibre Channel or Ethernet

(iSCSI) to provide connectivity between hostsand

storage. In either case, the storage is physically

decoupled from the hosts. The SAN is often

built on a dedicated network fabric that is

separated from the LAN network to ensure the

latency-sensitive block I/O

SAN traffic does not interfere with the traffic

on the LAN network. This examples shows an

dedicated SAN network connecting multiple

application servers, database servers, NAS

filers on

one side, and a number of disk systems andtape drive system on the other. The servers and

the

storage devices are connected together by the

SAN as peers.


6/8

Storage Area Network Components

As previously discussed, the primary

technology used in storage area networks

today is Fibre Channel. This section provides a

basic overview of the components in a fibre

channel storage fabric as well as different

topologies and configurations open to

Windows deployments.

Fibre Channel Topologies

Fundamentally, fibre channel defines three

configurations:

Point-to-point

Fibre Channel Arbitrated Loop (FC-AL)

Switched Fibre Channel Fabrics (FC-SW).

Although the term fibre channel implies

some form of fibre optic technology, the fibre

channel specification allows for both fibre

optic interconnects as well as copper coaxial

cables.

Point-to-Point

Point-to-point fibre channel is a simple way to

connect two (and only two) devices directly

together, 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 scalable

enterprise configuration and we will not

consider it again in this document.

Arbitrated Loops

A fibre channel arbitrated loop is exactly what

it says; it is a set of hosts and devices that are

connected into a single loop, as shown inFigure 2 below. It is a cost-effective way to

connect up to 126 devices and hosts into a

single network.

Figure 2: Fibre Channel arbitrated loop

Devices on the loop share the media; each

device is connected in series to the next device

in the loop and so on around the loop. Any

packet traveling from one device to another

must pass through all intermediate devices. In

the example shown, for host A to

communicate with device D, all traffic

between the devices must flow through the

adapters 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

done at the physical layer by the fibre channel

interface card itself; it does not require

HostStorage

Host A Host B

Device

E

DeviceC

DeviceD


7/8

processing on the host or the device. This is

very analogous to the way a token-ring

topology operates.

Fibre Channel Switched Fabric

In a switched fibre channel fabric,devices are connected in a many-to-

many topology using fibre channel

switches, as shown in Figure 4 below.

When a host or device communicates

with another host or device, the

source and target setup a point-to-

point connection (just like a virtual

circuit) between them and

communicate directly with each

other. The fabric itself routes datafrom the source to the target. In a

fibre channel switched fabric, the

media is not shared. Any device can

communicate with any other device

(assuming it is not busy) and

communication occurs at full bus

speed (1Gbit/Sec or 2Gbit/sec today

depending on technology)

irrespective of other devices and

hosts communicating.

ConclusionSAN is a data centric network.It is

deployed over networks and devicesfor data management and enterprisegrowth where data security id ofmain concern. The storagenetworking has built a working areaand will come out with specifiationsand standard recommendations.

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 : //ww w .x iote ch.com/,

May

2004.

[4]IBMCorp.http://ww w .r e d books .ib m.c om/p

ubs/pdfs/ r edbo o k s/sg 2 4 5 4 7 0 .pdf, March

2003,

[5] EMC Corp.http://ww w .e mc.com/p r o ducts/storage_mana

g

ement/controlcenter/pdf/H1140_cntrlctr_srm_

plan_ds_ldv.pdf, May 2004.

Referenced websites:

1. IBM System Storage: Storage

area networks

http://www-

03.ibm.com/servers/storage/san/

2. Cisco

http://www.cisco.com

3. Brocade

http://www.brocade.com

D e v i ce

E

D e v i ce

H

D e v i ce

G

D e v i ce

F

D e v i ce

I

S w i tches F ib re Channe l Fab r ic

H os t A H os t B H os t C H os t D
http://www.xiotech.com/http://www.xiotech.com/http://www.xiotech.com/http://www.xiotech.com/http://www.xiotech.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.emc.com/products/storage_managhttp://www-03.ibm.com/servers/storage/san/http://www-03.ibm.com/servers/storage/san/http://www.cisco.com/http://www.brocade.com/http://www.xiotech.com/http://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.cisco.com/http://www.brocade.com/


8/8

4. QLogic

http://www.qlogic.com
http://www.qlogic.com/http://www.qlogic.com/

storages area networks

Documents