- Sun Storage Virtual Tape Library VTL User Guide
Advantages of VTL tape virtualization
6 VTL User Guide • May 2008 G • 96267
thatproduceintermittentornon‐sequentialI/O,suchasincrementalsandbackupsof
workstatio ns, arecopiedtotapeonlyafter the yhavebeenbackeduptodiskand
incorporatedintolarge,sequentialbackupsets.Th is approachusestapedrives
continuously,atclosetotheirmaximumthroughput.Thedrivesspendless
timeidle,
sincetheymountandrepositionlessoften.Fewerdrivesandtapesareneededfora
givenworkload.Devicesandmedia suffer lesswearandtear.
Improvedutilizationofbackupmedia
Tapevirtualizationletsyoucreateemulatedtapevolumesthataremorecloselysiz ed
totheaveragesizeofyourbackupmedia.Ifyoudonotdecidetousetapecaching
(see“A u t o m a t e d TapeCaching” onpage 12),yousetthemaximumcapacityofyour
virtualtapesto 50‐60GBorto
theaveragesizeofyourbackupjobs(whicheveris
larger).Thisapproac h minimizeswastedspaceinthe criticaldiskcache,wherethe
firstcop yofeachbackupjobisstored,andmakesamaximumnumberofcartridges
availableforbackupjobsatanygiventime.Yourcopy/vaultsoftwarecanthen
consolidatethesesmallervolumesontofull‐sizedphysicaltape cartridgesoutside
thebackupwindow.Ifyoualsoenlargethesizeofthelibrary,asdescribedbelow,
youcanaccomodatea larg ertotalnumberofthesesmallervirtualtapes.
Ifyouadopttapeca ch in g, youcannotsizevirtualtapesthisway,since,
asweshall
see,thediskandph y sic al ‐tapeimagesofthevirtualtapemustbelogicallyidentical.
Larger,moreflexiblelibraries
TheSun VTL virtuallibraryfaithfullyemulate saSunL700physical tapelibrary.
But,whiletheL700has678slots ,theSun V TL canhaveupto64000inanon‐tape
cachingsolution,dependingonthebackupapplicati o n(see“A u t o m a t e d Tape
Caching”on page 12). Thisisaparticul ar ly importantconsiderationifyou
improve
mediautilizationbyreducingthesizeofyourvirtualtapevolumes,asdescribed
above.Onelargevirtuallibrarycan,on itsown,servealltheneedsofabackup
applicationmasterserver.
CompatibilitywithACSLS managementsoftware
Tapevirtualizationletsyoucontro ldisk‐basedvirtuallibrarieswiththe same
industry‐standard,SunACSLSsoftwarethatcontrolsphysicaltape libraries.ACS LS
addsanad dit ional virtualizationlayertoyourbackupenvironment,further
reducingdisruptionstoestablishedinfrastructure an d polici eswhile,atthesame
time,bringingnewcapabili t ies.