VMware GSX Server 2.5.2

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• 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, first disable SCSI reservations and make sure it 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 setting disk.locking = "true".

• If your host abnormally terminates or another action occurs that may require you to repair the plain disk, the virtual machine using the plain disk should be powered on and the disk repaired in one virtual machine before it is used in another virtual machine. This ensures that only one copy of the disk checker runs at one time.

• On a Windows host, 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"

  They should be reported periodically only on the passive node of the cluster and should also be reported when the passive node is taking over during a failover. The errors are reported 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.