HP SAN Virtualization Services Platform - Manual (Page 239)

Restoring from snapshots
Instant restore is an operation that replaces a virtual disk or VDG with a snapshot that was created
from the virtual disk or VDG. The original element is deleted, and only the snapshot remains. This
option is only enabled for a single snapshot created from a single PiT on a source element. If there
is more than one snapshot on the PiT, or more than one PiT on the source element, instant restore is
disabled.
Instant restore enables you to implement the following testing scenario:
1. Create a PiT on your source element (virtual disk or VDG) to freeze your starting point.
2. Create multiple snapshots from the PiT.
3. Test each snapshot with a different scenario, in order to discover the best solution.
4. Identify which snapshot has the best results.
5. Delete all other snapshots.
6. Restore the remaining snapshot, making this snapshot your new source element and deleting the
original element. The snapshot becomes a virtual disk and maintains its name.
To restore a virtual disk or VDG from a snapshot:
1. Take the application using the virtual disk or VDG offline.
CAUTION:
Do not restore a snapshot while the application using the source element is online, because
the data integrity is not maintained, since the process makes the server cache obsolete by
replacing the contents of the volume. Just before restoring, the application is presented with
the data of the original element (virtual disk or VDG). Immediately after restoring the
snapshot, the application will be presented with the data of the selected snapshot which
was restored. Also, the original element is deleted, and the snapshot becomes a virtual disk
or a VDG which maintains the snapshot name. On the host side, follow the instructions in
the operating system-specific VSM host agent user manual for restoring a snapshot.
2. Right-click the snapshot or VDG snapshot with which you want to replace the virtual disk or VDG.
3. Select Manage > Snapshot Service > Instant Restore. A confirmation screen appears.
4. Read the confirmation screen and check that you want to perform the operation described.
5. If you decide you do not want to proceed with the restore operation, click Cancel. Otherwise,
click Finish and the original virtual disk or VDG is deleted and replaced with the snapshot or
VDG snapshot, which is now a virtual disk or VDG.
Planning storage pool capacity for snapshots and PiTs
Snapshot PiTs and snapshots require storage capacity. Whenever you create a PiT or snapshot, a
temporary virtual disk is created to hold modifications to the element on which you created the PiT or
to the snapshot that you created. Each PiT requires an initial capacity of 512 MB, and can grow with
time to be equal to the size of the original virtual disk on which you created the PiT. This happens
when you completely overwrite the source element with new information.
When planning the capacity you require in each storage pool, consider:
SAN Virtualization Services Platform Manager User Guide 239