There are four components to the VSS framework: Requestor, Writer, Provider, and the Volume Shadow Copy Service itself.
Table: VSS framework components
Component
Action
Volume Shadow Copy Service
Talks to and coordinates the Requestor, Provider, and Writer.
Requestor
As a Requestor, the vxsnap component of FlashSnap notifies the VSS coordinator to initiate the VSS request to prepare the SQL Server instance for quiescing and later requests that the snap shot process begin.
Writer
As Writers, VSS-enabled applications such as SQL Server respond to requests to prepare and participate in the generation of snapshots, provide success/failure status, and provide information about the application including what is to be backed up and restored, and restore strategy.
Provider
As a Provider, FlashSnap creates the persistent snapshot.
