A VSS instant restore operation restores data by using a hardware-assisted restore method. A FlashCopy operation is an example of a hardware-assisted restore method.
The key component of producing a VSS instant restore is the speed with which the application can become operational with the data that is stored on local shadow volumes. Even though the data is restored relatively quickly, the transaction logs must be replayed after the restore. The time of recovery for the Exchange database increases as the number of logs to be replayed increases.
A VSS instant restore is only possible when all of the data from the database that is specified for restore is on storage subsystems that are supported by the VSS instant restore. If part of the data that is restored, including the log files, is on a local disk, a VSS fast restore is completed.
When you perform VSS instant restores, make sure that any previous background copies that include a copy of a volume that is being restored are completed before you initiate the VSS instant restore. However, this check is not necessary for XIV®, SAN Volume Controller, or Storwize® V7000 with space-efficient target volumes.
You cannot complete a partial restore by using the /partial option when a VSS instant restore is completed. Although Data Protection for Exchange allows this operation to begin, it either fails or completes incorrectly. If you restore only one database from a VSS backup that is stored on local VSS shadow volumes on DS8000®, SAN Volume Controller, Storwize V7000, or XIV, set the InstantRestore option to False in the Restore Options pane in the Recover tab of the Data Protection for Exchange GUI, or specify /instantrestore=no on the command-line interface.
VSS instant restore capability is automatically disabled when a restore is completed to an Exchange recovery database.
VSS instant restore is the default restore method when all data specified for a restore is on storage subsystems that are supported by the VSS instant restore. A failover to VSS fast restore can still occur when an error is detected early enough in the VSS instant restore process to trigger the failover. In this situation, an error is logged in the dsmerror.log file. The dsmerror.log file is used by the DSMAGENT. However, a failover to VSS fast restore might not always be possible. For example, if an error occurs later in the restore process, VSS instant restore processing fails without a failover to VSS fast restore. An error can be a pending background copy on the storage subsystem, a failure to start the FlashCopy® operation on the snapshot provider system, or other hardware error.
When you plan for VSS instant restore, backups can only be restored to the same DS8000, SAN Volume Controller, XIV, or Storwize V7000 storage subsystem from which they are backed up.
The list of devices that support instant restore is maintained online at http://www.ibm.com/support/docview.wss?uid=swg21455924.