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FlashSnap integrates with Volume Shadow Copy Service as both a VSS Requestor and a VSS Provider.
The following steps occur, in the order presented, during the snapshot process:
Acting as a VSS Requestor, FlashSnap notifies the VSS coordinator service to prepare for a split-mirror snapshot of a SQL Server instance.
The VSS coordinator service calls the SQL Server VSS Writer to find out which volumes contain the databases and transaction logs.
The VSS coordinator service notifies the FlashSnap VSS Provider to prepare for the snapshot.
Acting as a VSS Requestor, FlashSnap requests that the VSS coordinator service begin the snapshot call.
The VSS coordinator service notifies the SQL Server VSS Writer to quiesce and freeze the databases in preparation for the snapshot. When this is accomplished, the SQL Server Writer informs the VSS coordinator service to proceed.
The VSS coordinator service calls the FlashSnap Provider to create the split-mirror snapshot by detaching the snapshot volume from the original volume. The snapshot process takes a maximum of 10 seconds. After the snapshot volume is detached, the FlashSnap Provider informs the VSS coordinator service to proceed.
The VSS coordinator service notifies the SQL Server VSS Writer to thaw (release the freeze) and resume normal I/O.
The following steps occur, in the order presented, during the restore process:
Acting as a VSS Requestor, FlashSnap notifies the VSS coordinator service to prepare for a restore operation.
The VSS coordinator service calls the SQL Server VSS Writer, which prepares for the restore operation.
The FlashSnap utility restores the snapshot volumes. After the snapback operation completes, the FlashSnap utility informs the VSS coordinator service to proceed.
The VSS coordinator service notifies the SQL Server VSS Writer to process the post-restore operations.