Lenovo ThinkServer RD650 - Page 85

•RAID1:mirroringwithoutparityorstriping
RAID1usesmirroringsothatdatawrittentoonedriveissimultaneouslywrittentoanotherdrive.Thisis
goodforsmalldatabasesorotherapplicationsthatrequiresmallcapacitybutcompletedataredundancy.
RAID1providesfaulttolerancefromdiskerrorsorfailuresandcontinuestooperateaslongasatleast
onedriveinthemirroredsetisfunctioning.Withappropriateoperatingsystemsupport,therecanbe
increasedreadperformanceandonlyaminimalwriteperformancereduction.
RAID1requiresaminimumnumberoftwoharddiskdrives.
•RAID5:block-levelstripingwithdistributedparity
RAID5usesdiskstripingandparitydataacrossalldrives(distributedparity)toprovidehighdata
throughput,especiallyforsmallrandomaccess.RAID5distributesparityalongwiththedataandrequires
alldrivesbutonetobepresenttooperate;drivefailurerequiresreplacement,butthearrayisnot
destroyedbyasingledrivefailure.Upondrivefailure,anysubsequentreadoperationscanbecalculated
fromthedistributedparitysothatthedrivefailureismaskedfromtheenduser.Thearraywillhavedata
lossintheeventofaseconddrivefailureandisvulnerableuntilthedatathatwasonthefailingdriveis
rebuiltontoareplacementdrive.Asingledrivefailureinthesetwillresultinreducedperformanceof
theentiresetuntilthefailingdrivehasbeenreplacedandrebuilt.
RAID5requiresaminimumnumberofthreeharddiskdrives.
•RAID6:block-levelstripingwithdistributedparity
RAID6usesdistributedparity,withtwoindependentparityblocksperstripe,anddiskstriping.ARAID6
virtualdrivecansurvivethelossofanytwodriveswithoutlosingdata.ARAID6drivegroupissimilar
toaRAID5drivegroup.Blocksofdataandparityinformationarewrittenacrossalldrives.Theparity
informationisusedtorecoverthedataifoneortwodrivesfailinthedrivegroup.
RAID6requiresaminimumnumberofthreeharddiskdrives.
•RAID10:acombinationofRAID0andRAID1
RAID10consistsofstripeddataacrossmirroredspans.ARAID10drivegroupisaspanneddrive
groupthatcreatesastripedsetfromaseriesofmirroreddrives.RAID10allowsamaximumofeight
spans.YoumustuseanevennumberofdrivesineachRAIDvirtualdriveinthespan.TheRAID1
virtualdrivesmusthavethesamestripesize.RAID10provideshighdatathroughputandcompletedata
redundancybutusesalargernumberofspans.
RAID10requiresaminimumnumberoffourharddiskdrivesandalsorequiresanevennumberofdrives,
forexample,sixharddiskdrivesoreightharddiskdrives.
•RAID50:acombinationofRAID0andRAID5
RAID50usesdistributedparityanddiskstriping.ARAID50drivegroupisaspanneddrivegroupin
whichdataisstripedacrossmultipleRAID5drivegroups.RAID50worksbestwithdatathatrequires
highreliability,highrequestrates,highdatatransfers,andmedium-to-largecapacity.
Note:HavingvirtualdrivesofdifferentRAIDlevels,suchasRAID0andRAID5,inthesamedrivegroupis
notallowed.Forexample,ifanexistingRAID5virtualdriveiscreatedoutofpartialspaceinanarray,the
nextvirtualdriveinthearrayhastobeRAID5only.
RAID50requiresaminimumnumberofsixharddiskdrives.
•RAID60:acombinationofRAID0andRAID6
RAID60usesdistributedparity,withtwoindependentparityblocksperstripeineachRAIDset,anddisk
striping.ARAID60virtualdrivecansurvivethelossoftwodrivesineachoftheRAID6setswithout
losingdata.RAID60worksbestwithdatathatrequireshighreliability,highrequestrates,highdata
transfers,andmedium-to-largecapacity.
RAID60requiresaminimumnumberofsixharddiskdrives.
Chapter5.Configuringtheserver69