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Chapter 3. Advanced Technologies over Multiservice Provisioning Platforms

Chapter 3. Advanced Technologies over Multiservice Provisioning Platforms

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Figure3-2.DWDMfromanMSPP



[Viewfullsizeimage]



Therefore,whentheterminology"advancedtechnologiesover

MSPP"isused,youmighthavetoreprogramyourthinkingto

gobeyondsimplySONETencapsulationofservicestothatof

anyservicethatcanbelaunchedfromtheMSPPplatform.

Thischaptercoversthreemajoradvancedtechnologies:

Storage-areanetworking(SAN)

DWDM

Ethernet

Foreach,youwilllookatabriefhistoryoftheevolutionofthe

serviceingeneralandthenfocusontheirintegrationintothe

MSPPplatform.



Storage

ITorganizationshavebeenwrestlingoverwhetherthe

advantagesofimplementingaSANsolutionjustifythe

associatedcosts.Otherorganizationsareexploringnewstorage

optionsandwhetherSANreallyhasadvantagesovertraditional

storageoptions,suchasNetworkAttachedStorage(NAS).In

thisbriefhistoricaloverview,youwillbeintroducedtothebasic

purposeandfunctionofaSANandwillexamineitsrolein

modernnetworkenvironments.YouwillalsoseehowSANs

meetthenetworkstorageneedsoftoday'sorganizations.

Whenthelayersofeventhemostcomplextechnologiesare

strippedback,youwilllikelyfindthattheyarerootedin

commonrudimentaryprinciples.Thisiscertainlytrueof

storage-areanetworks(SANs).Behindtheacronymsandfancy

terminologyliesatechnologydesignedtoprovideawayof

offeringoneoftheoldestnetworkservicesofprovidingdatato

userswhoarerequestingit.

Inverybasicterms,aSANcanbeanythingfromapairof

serversonanetworkthataccessacentralpoolofstorage

devices,asshowninFigure3-3,tomorethanathousand

serversaccessingmultimillionsofmegabytesofstorage.

Theoretically,aSANcanbethoughtofasaseparatenetworkof

storagedevicesthatarephysicallyremovedfrombutstill

connectedtothenetwork,asshowninFigure3-4.SANs

evolvedfromtheconceptoftakingstoragedevicesand,

therefore,storagetrafficfromthelocal-areanetwork(LAN)and

creatingaseparateback-endnetworkdesignedspecificallyfor

data.



Figure3-3.ServersAccessingaCentralPoolof

StorageDevices



Figure3-4.SAN:APhysicallySeparateNetwork

AttachedtoaLAN



ABriefHistoryofStorage

SANsrepresentthelatestofanemergingsequenceofphasesin

datastoragetechnology.Inthissection,youwilltakealookat

theevolutionofDirectAttachedStorage,NAS,andSAN.Just

keepinmindthat,regardlessofthecomplexity,onebasic

phenomenonisoccurring:clientsacquiringdatafromacentral

repository.Thisevolutionhasbeendrivenpartlybythe

changingwaysinwhichusersusetechnology,andpartlybythe

exponentialincreaseinthevolumeofdatathatusersneedto

store.Ithasalsobeendrivenbynewtechnologiesthatenable

userstostoreandmanagedatainamoreeffectivemanner.

Whenmainframeswerethedominantcomputingtechnology,

datawasstoredphysicallyseparatefromtheactualprocessing

unitbutwasstillaccessibleonlythroughtheprocessingunits.

Aspersonalcomputing-basedserversproliferated,storage

devicesmigratedtotheinteriorofthedevicesorinexternal

boxesthatwereconnecteddirectlytothesystem.Eachofthese

approacheswasvalidinitstime,butwithusers'growingneed

tostoreincreasingvolumesofdataandmakethatdatamore

accessible,otheralternativeswereneeded.Enternetwork

storage.

Networkstorageisagenerictermusedtodescribenetworkbaseddatastorage,butmanytechnologieswithinitmakethe



sciencehappen.Thenextsectioncoverstheevolutionof

networkstorage.



DirectAttachedStorage

Traditionally,onclient/serversystems,datahasbeenstoredon

devicesthatareeitherinsideordirectlyattachedtotheserver.

Simplystated,DirectAttachedStorage(DAS)referstostorage

devicesconnectedtoaserver.Allinformationcomingintoor

goingoutofDASmustgothroughtheserver,soheavyaccess

toDAScancauseserverstoslowdown,asshowninFigure3-5.



Figure3-5.DirectAttachedStorageExample



InDAS,theserveractsasagatewaytothestoreddata.Nextin

theevolutionarychaincameNAS,whichremovedthestorage

devicesfrombehindtheserverandconnectedthemdirectlyto

thenetwork.



NetworkAttachedStorage

NetworkAttachedStorage(NAS)isadata-storagemechanism

thatusesspecialdevicesconnecteddirectlytothenetwork

media.ThesedevicesareassignedanInternetProtocol(IP)

addressandcanthenbeaccessedbyclientsusingaserverthat



actsasagatewaytothedataor,insomecases,allowsthe

devicetobeaccesseddirectlybytheclientswithoutan

intermediary,asshowninFigure3-6.



Figure3-6.NAS



ThebenefitoftheNASstructureisthat,inanenvironmentwith

manyserversrunningdifferentoperatingsystems,storageof

datacanbecentralized,ascanthesecurity,management,and

backupofthedata.Anincreasingnumberofbusinessesare

alreadyusingNAStechnology,ifonlywithdevicessuchasCDROMtowers(standaloneboxesthatcontainmultipleCD-ROM

drives)thatareconnecteddirectlytothenetwork.

SomeoftheadvantagesofNASincludescalabilityandfault

tolerance.InaDASenvironment,whenaservergoesdown,the

datathattheserverholdsisnolongeravailable.WithNAS,the

dataisstillavailableonthenetworkandisaccessiblebyclients.

Aprimarymeansofprovidingfault-toleranttechnologyis

RedundantArrayofIndependent(orInexpensive)Disks(RAID),

whichusestwoormoredrivesworkingtogether.RAIDdisk



drivesareoftenusedforservers;however,theiruseinpersonal

computers(PCs)islimited.RAIDcanalsobeusedtoensure

thattheNASdevicedoesnotbecomeasinglepointoffailure.



Storage-AreaNetworking

Storage-areanetworking(SAN)takestheprincipleonestep

furtherbyallowingstoragedevicestoexistontheirown

separatenetworkandcommunicatedirectlywitheachother

oververyfastmedia.Userscangainaccesstothesestorage

devicesthroughserversystems,whichareconnectedtoboth

thelocal-areanetwork(LAN)andtheSAN,asshowninFigure

3-7.



Figure3-7.ASANwithInterconnectedSwitches



ThisisincontrasttotheuseofatraditionalLANforprovidinga

connectionforserver-basedstorage,astrategythatlimits

overallnetworkbandwidth.SANsaddressthebandwidth

bottlenecksassociatedwithLAN-basedserverstorageandthe

scalabilitylimitationsfoundwithSmallComputerSystems

Interface(SCSI)bus-basedimplementations.SANsprovide

modularscalability,highavailability,increasedfaulttolerance,

andcentralizedstoragemanagement.Theseadvantageshave



ledtoanincreaseinthepopularityofSANsbecausetheyare

bettersuitedtoaddressthedata-storageneedsoftoday'sdataintensivenetworkenvironments.



BusinessDriversCreatingaDemandforSAN

Severalbusinessdriversarecreatingthedemandand

popularityforSANs:

RegulationsRecentnationaldisastershavedriven

regulatoryauthoritiestomandatenewstandardsfor

disasterrecoveryandbusinesscontinuanceacrossmany

sectors,includingfinancialandbanking,insurance,health

care,andgovernmententities.Asanexample,theFederal

ReserveandtheSecuritiesandExchangeCommission

(SEC)recentlyreleasedadocumenttitledInteragency

PaperonSoundPracticestoStrengthentheResilienceof

theU.S.FinancialSystem,whichoutlinesobjectivesfor

rapidrecoveryandtimelyresumptionofcriticaloperations

afteradisaster.Similarregulationsaddressingspecific

requirementsforhealthcare,lifesciences,andgovernment

havebeenissuedorareunderconsideration.

CostFactorsincludethecostofdowntime(millionsof

dollarsperhourforsomeinstitutions),moreefficientuseof

storageresources,andreducedoperationalexpenses.

CompetitionWithcompetitivepressurescreatedby

industryderegulationandglobalization,manybusinesses

arenowbeingjudgedontheirbusinesscontinuanceplans

morecloselythanever.Manycustomersbeingcourtedare

requestingdocumentationdetailingdisaster-recoveryplans

beforetheyselectprovidersorevenbusinesspartners.

Beinginapositiontorecoverquicklyfromanunplanned

outageorfromdatacorruptioncanbeavitalcompetitive



differentiatorintoday'smarketplace.Thisrapidrecovery

capabilitywillalsohelpmaintaincustomerandpartner

relationshipsifsuchaneventdoesoccur.

TheadvantagesofSANsarenumerous,butperhapsoneofthe

bestexamplesisthatoftheserverlessbackup(alsocommonly

referredtoasthird-partycopying).Thissystemallowsadisk

storagedevicetocopydatadirectlytoabackupdeviceacross

thehigh-speedlinksoftheSANwithoutanyinterventionfroma

server.DataiskeptontheSAN,whichmeansthatthetransfer

doesnotpollutetheLAN,andtheserver-processingresources

arestillavailabletoclientsystems.

SANsaremostcommonlyimplementedusingatechnology

calledFibreChannel(FC).FCisasetofcommunication

standardsdevelopedbytheAmericanNationalStandards

Institute(ANSI).Thesestandardsdefineahigh-performance

data-communicationstechnologythatsupportsveryfastdata

ratesofmorethan2Gbps.FCcanbeusedinapoint-to-point

configurationbetweentwodevices,inaringtypeofmodel

knownasanarbitratedloop,andinafabricmodel.

DevicesontheSANarenormallyconnectedthroughaspecial

kindofswitchcalledanFCswitch,whichperformsbasicallythe

samefunctionasaswitchonanEthernetnetwork:Itactsasa

connectivitypointforthedevices.BecauseFCisaswitched

technology,itiscapableofprovidingadedicatedpathbetween

thedevicesinthefabricsothattheycanusetheentire

bandwidthforthedurationofthecommunication.

Regardlessofwhetherthenetwork-storagemechanismisDAS,

NAS,orSAN,certaintechnologiesarecommon.Examplesof

thesetechnologiesincludeSCSIandRAID.

Foryears,SCSIhasbeenprovidingahigh-speed,reliable

methodofdatastorage.Overtheyears,SCSIhasevolved

throughmanystandardstothepointthatitisnowthestorage



technologyofchoice.RelatedtobutnotreliantonSCSIisRAID.

RAIDisaseriesofstandardsthatprovideimproved

performanceandfaulttolerancefordiskfailures.Such

protectionisnecessarybecausedisksaccountforabout50

percentofallhardwaredevicefailuresonserversystems.As

withSCSI,thetechnologiessuchasRAIDusedtoimplement

datastoragehaveevolved,developed,andmaturedoverthe

years.

ThestoragedevicesareconnectedtotheFCswitchusingeither

multimodeorsingle-modefiber-opticcable.Multimodecableis

usedforshortdistances(upto2km),andsingle-modecableis

usedforlongerdistances.Inthestoragedevicesthemselves,

specialFCinterfacesprovidetheconnectivitypoints.These

interfacescantaketheformofbuilt-inadapters,whichare

commonlyfoundinstoragesubsystemsdesignedforSANs,or

canbeinterfacecardsmuchlikeanetworkcard,whichare

installedintoserversystems.

Sohowdoyoudeterminewhetheryoushouldbemoving

towardaSAN?Ifyouneedtocentralizeorstreamlineyourdata

storage,aSANmightberightforyou.Ofcourse,thereisone

barrierbetweenyouandstorageheaven:money.SANsremain

thedomainofbigbusinessbecausethepricetagofSAN

equipmentislikelytoremainataleveloutsidethereachof

smallorevenmedium-sizebusinesses.However;ifpricesfall

significantly,SANswillfindtheirwayintoorganizationsof

smallersizes.



EvolutionofSAN

TheevolutionofSANisbestdescribedinthreephases,eachof

whichhasitsownfeaturesandbenefitsofconfiguring,

consolidating,andevolution:

PhaseIConfiguresSANsintohomogeneousislands,as



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