Specifications

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VMware GSX Server Administration Guide
Issues to Consider When Sharing Disks
• Do not try to share a disk among multiple running virtual machines that are not
collocated on the same host. The disk file itself may be located remotely, but the
virtual machines must be running together on the same GSX Server host. If you
try to share a disk among virtual machines located on different hosts, you could
encounter the same unpredictable results you would expect to find if you
disabled disk locking.
• If only one running virtual machine is using a given disk, and it is running
applications that do not use SCSI reservation, then the disk’s performance might
be degraded slightly.
• At this time, if one virtual machine does not have SCSI reservation enabled for its
virtual disk, but another virtual machine does have SCSI reservation enabled for
the same virtual disk, GSX Server does allow the disk to be shared. However, any
virtual machine not configured for SCSI reservation that tries to access this disk
concurrently can cause corruption or data loss on the shared disk. VMware
recommends you take care when sharing disks.
• If you need to shrink or defragment the virtual disk (provided it is not a
preallocated virtual disk or a physical disk), first disable SCSI reservations and
make sure the virtual disk is not being used by any other virtual machine. To
disable SCSI reservation for a virtual machine, open the configuration file and
comment out or remove the scsi[n].sharedBus = "virtual" line
and make sure the disk.locking line is set to "true".
• If your host abnormally terminates or another action occurs that may require you
to repair the preallocated virtual disk, power on the virtual machine using the
virtual disk and repair the disk in one virtual machine before using it in another
virtual machine. Doing these steps ensures that only one copy of the disk
checker runs at one time.
• In a Windows virtual machine, some disk errors are recorded in the Windows
event log in normal operation. These error messages have a format similar to
"The driver detected a controller error on
\Device\Scsi\BusLogic3"
The errors should appear in the log periodically only on the passive node of the
cluster and should also appear when the passive node is taking over during a
failover. The errors are logged because the active node of the cluster has
reserved the shared virtual disk. The passive node periodically probes the shared
disk and receives a SCSI reservation conflict error.