Setup Guide

Best Practices 73
Restore VM Metadata to Recover VMs from a Snapshot
1 Access the Backup, Update and Restore menu in the local console on the
XenServer host or pool master.
2 Perform a metadata restoration operation using the Restore Virtual
Machine Metadata
menu option. The metadata restoration operation can
restore only VM records associated with the selected SR, or all of the VM
records found potentially from other SRs which were present at the time of
the backup.
NOTE: There is also an option to test which VMs are imported without
actually performing the restoration operation.
Adjusting SCSI Timeouts to Tolerate Storage
Controller Failures
To account for time that an IO may take to complete in a case where the
PowerVault MD3000 or MD3000i storage arrays goes through exception
recovery on I/O operations, it is recommended to adjust the SCSI timeouts
on XenServer hosts and virtual machines that are resident on the SRs on
PowerVault MD3000 or MD3000i storage arrays.
Adjusting SCSI Timeouts for PowerVault MD3000 RAID Enclosure
If the XenServer host is connected to PowerVault MD3000 RAID enclosure,
adjust the SCSI timeout on Microsoft Windows VMs residing on the SR
resident on the PowerVault MD3000 RAID enclosure by changing the
following registry setting:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\disk\T
imeOutValue.
The value needs to be created if not present. Set this value to 200.
Do not modify the SCSI timeout in paravirtualized Linux VMs as the VM
virtual disks are not presented as SCSI disks.