- Sun Storage Virtual Tape Library VTL User Guide

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CHAPTER
1
Introduction:VTLappliancesand
enterprisedata‐protection
SunStorageTekVirtualTapeLibrary(VTL)technologymakesthebenefitsofdisk‐to‐
disk‐to‐tapearchitectureavailabletocomplex backupenvironmentsthatcannot 
readilyaccommodatethedisruptionsandadministrativeburdensthatoften
accompanymajorchangestoinformation‐managementenvironm entsandprocesses.
VTLsol uti ons makediskmediaavailabletoapplicationsthatare
configuredtowork
withtape.VTLsoftwarepresentsyourexistingtape‐centricbackuparchitecturewith
whatappeartobe familiar tapelibra rie s, drives,anddatacartridgeswhilemanaging
thecomplexitiesoftheimplementation—diskarrays,RAIDgroups,andlogical
volumes—internally.
Suchtransparencyisa bso lutely criticalwhenbackupisjustoneaspect
ofan
enterprise‐widebusiness‐continuityplan.Whenlegacysystemsand multiple,
interdependentapplications,procedures,policies,and/orserviceprovider sare
involved,evenmodestchangestoabackuparchitecturecan haveunforeseen,far‐
reachingconsequences.
Theadvantagesthatdisk‐to‐diskbackuphastoofferarenolesscriticalincomplex
environments.
Heavyworkloads,tightschedules,andmultipledependenciesoften
makebackupwindowsverytightornon‐existent.Jobsthatfailto completecannot,
inmostcases,beretried.Tape‐basedbackupsystemsperformwellwhenhandling
bigjobs,likefullbackupsoflargefilesandfilesystemsthat canstreamlarge
amountsofsequentialdata.Butmuchofthe currentbackupworkloadconsistsof
intermittent,essentiall y randomI/O—incrementals,fullbackupsofheterogeneous
smallserversandworkstations,andsmallfiles(suchas thoseassociatedwithemail
systems).Tapedrivesperformpoorlyundertheseconditions.Butdisk‐basedstorage
isideallyplacedtohandle
thistypeofI/O.
Theremainderofthischapterprovides:
■ abriefsummaryofVTL“Features”onpage 2
■ adetaileddiscussionofthe“A d v a n t a g e s ofVTLtapevirtualization”onpage 4
■ amorein‐depthlookatselected,“KeyVTLfeaturesandoptions”onpage 8.