HP StorageWorks SAN Virtualization Services Platform Administrator Guide (5697-0934, May 2011)

10. Remove the VSS shadow copy by typing vshadow.exe -ds={SnapShotID} and pressing
Enter.
The vshadow.exe -ds={SnapShotID} command unmounts the snapshot on the host and
deletes the snapshot and PiT on the VSM.
11. To create a persistent VSS shadow copy with a snapshot that can be presented to another
host, type vshadow.exe -p -t=export.xml m: and press Enter.
The vshadow.exe -p -t=export.xml m: command creates a shadow set that you can
transport to another host. VSS generates a backup component document, which is
export.xml, that you can use for introducing the shadow set to another host by using the
import option.
12. To import a shadow set to another host, type vshadow -i=export.xml on the host into
which you are importing the shadow set and press Enter.
Integrating VSS with asynchronously mirrored VSM virtual disks
When VSM receives a request to create a VSS snapshot on an asynchronously mirrored virtual
disk, VSM handles this as a request to create a user PiT, with a snapshot, on that virtual disk.
Creating a user PiT for the VSS request indicates that this PiT was taken while the application was
in backup mode. However, the snapshot that is created in order to comply with VSS requirements,
prevents the mirror from progressing. The mirror cannot delete older PiTs because the snapshots
use the older PiTs. The mirror also cannot create new PiTs because the older PiTs exist.
The solution to correct this situation is to create the PiT using VSS and delete the snapshot after the
snapshot is created to allow the asynchronous mirror to progress. You can achieve this solution
by using the Vshadow utility to create non-persistent shadow copies. An example of the command
to create a non-persistent shadow copy for drive m: is vshadow.exe m:.
If the application uses multiple drives, you must include all of the drives in the command.
To run this command several times, at predefined intervals, place the command into a command
file, and configure the Windows scheduler to run the command file at the required intervals.
When the Vshadow utility completes running this command, the shadow copy that the Vshadow
utility created for drive m:\ is deleted. On VSM, however, the user PiT that was created remains.
Only the snapshot that vshadow created for the user PiT is deleted. As long as the user PiT remains
in the system, the you can create a snapshot on it, and present the snapshot to the server for
recovery. The user PiT is eventually deleted according to the operation rules for asynchronous
mirrors.
Integrating VSS with backup software
A backup solution involves these components:
• Backup server
• Backup client or clients
• Backup media servers
The backup server runs the backup software and manages the backup process by communicating
with the backup agents and the media servers. Backup clients negotiate with the applications and
prepare the data for backup. The media servers take the data that the backup agent prepared
and write the data to tapes or disks.
To implement a solution with servers that use the VSM virtual disks, through DPMs, you must expose
the application servers and the media servers to the SAN CLI virtual disk and install the SVSP VSS
storage provider on the backup client server where the application, the writer, exists. Exposing
the servers to the SAN CLI virtual disk makes the servers ready to service the VSS command that
the backup software initiates.
74 Microsoft Volume Shadow Copy Service