2.0

Table Of Contents
VMware, Inc. 289
Chapter 13 Configuring Clustering on Windows Hosts
SCSI Reservation Prerequisites and Restrictions
TheuseofSCSIreservationisrestrictedasfollows:
YoucanenableSCSIreservationonlyforvirtualSCSIdisks.Youcannotenable
SCSIreservationforadiskthatisconfiguredasapassthrough(generic)SCSI
device.
VMwareServersupportsSCSIreservationonlywithpreallocatedvirtualdisks.
Whenyoucreateanewvirtualmachine,oraddanewvirtualdisktoanexisting
virtualmachine,configureapreallocatedvirtualdiskwhenusingSCSI
reservation.SupportforSCSIreservationwithgrowablevirtualdisksisnot
supported.
DisksusingSCSIreservationcanbesharedonlyamongvirtualmachinesrunning
onthesameVMwareServerhost.Ifyoutrytoshareadiskamongvirtualmachines
locatedondifferenthosts,datalossorcorruptionislikely.Theshareddiskordisks
canbelocatedinanyvaliddatastore.
Donotshareadiskonthebootdisk,typicallySCSIbus0.Instead,useSCSI
reservationonadatadisklocatedonadifferentbus.Ifyousharethebootdisk,you
runtheriskofcorruptingit,becausethebootprogramisnotawarethatthediskis
being
sharedandcanwritetothediskregardlessofwhetherornotitisbeing
shared.
AvirtualSCSIdiskcanbestoredonanytypeofphysicalharddisk,includingIDE,
SCSI,andSATAphysicaldisks.
IfonevirtualmachinedoesnothaveSCSIreservationenabledforitsvirtualdisk,
butanothervirtualmachinedoeshaveSCSIreservationenabledforthesame
virtualdisk,VMwareServerstillallowsthedisktobeshared.However,thevirtual
machinethatisnotconfiguredforSCSIreservationcanaccessthe
shareddisk
concurrently,potentiallycausingdatalossorcorruption.
VMwareServervirtualmachinescurrentlysupportonlytheSCSI2disk
reservationprotocol,andnotapplicationsusingSCSI3diskreservations.
Enabling SCSI Reservation
SCSIreservationmustbeenabledineachvirtualmachinebeforeyoucansharevirtual
disks.
VMwarerecommendsthatyouconfiguresharedvirtualdisksonthesameSCSIbus,
whichmustbeadifferentbusfromtheonethattheguestoperatingsystemuses.For
example,ifyourguestoperatingsystemis
onthescsi0bus,configuretheshareddisks
onthenextavailablebus,typicallythescsi1bus.