Specifications

System Drives and System Drive Groups
28 SGI InfiniteStorage NAS Server and Titan Server
TheSMUcannotgrouporungroupsystemdrivesthatareusedinopen
StoragePools.AStoragePoolisopenifithasanyfilesystemthatismounted
orisbeingcheckedorfixedanywhereonthecluster.
DuringEVSmigration,theSMUautomaticallycopiesthegroupsfromthe
source
storageserverorclusterandaddsthemtothetargetstorageserveror
cluster.
SeeManagingSystemDriveGroups,onpage34forinformationoncreating
andmodifyingsystemdrivegroups.
SD Groups and Read Balancing
Whenperformingreadoperations,iftheservercanreadfilesystemdatathat
hasbeendistributedacrosstheSDgroups,thereadoperationsaremore
efficientanddiskheadmovementmaybedecreased.These benefitsoccur
becausethedataisdistributedacrossdifferentphysicaldisksintheSDs
makingupthe
SDgroupinsteadofbeingonthesamephysicaldisksmaking
uptheSDsoftheSDgroup.
Typically,filesystemdataisdistributedacrosstheSDsinaStoragePool
duringnormalwriteoperationsduetodynamicwritebalancing.However,
afteraddingSDstoanSDgrouporextending
aStoragePoolbyaddingSDs
thatresideonanew/differentphysicalstoragesubsystem,youmaywantto
manuallyinitiateadataredistributionsothatthefilesystem’sdataisevenly
spreadamongallSDsintheSDgroup.
Duringsuchadataredistribution,theserver’sfileservingperformancemay
be
impacted,becausetheserverisreadingandwritingdatafromthedata
distributionaswellasdatafromexternalrequests.
Thefilesystemdataredistributionutilityiscontrolledusingthe
fs-read-
balancer
command,andaseparatecommand,fs-sdg-utilization,isused
toseeareportonhowafilesystemisutilizingeachSDgroupinthe
underlyingStoragePool.Formoreinformationaboutthesecommands,refer
totheCommandLineReference.
Note:Afterafilesystemhasbeenexpandedtousenewstorage,youcanspread
thefile
systemʹsdataintothenewstorag ebyrunningthefilesystemdata
redistributionutility.Spreadingthedataintothenewstoragespreadstheread
loadacrossallofthefilesystem’sphysicaldisks,whichimprovesread
performance.
ReadBalancingUtilityConsiderations
Runningthefilesystemdataredistributionutilitycausesdata
tobere‐written
toanewlocation,whichwillbetheleast utilizedSDgroups(thenewstorage)
resultinginmorebalancedutilizationofSDgroups.
Note:Thefilesystemdataredistributionutilitycanberunonlyafter
expandingthefilesystemintothenewstorage,butitshouldbe
run
immediatelyanditmayberunonlyonce.Ifyourunthedataredistribution
utilitymorethanonce,orafteranapplicationhaswrittenasignificantamount
ofdataintotherecentlyaddedstorage,theutilitywilleitherrefusetorunor
produceunpredictableresults.