With Data Protection for Microsoft Exchange, you can manage and configure storage management policy for backups. A backup policy determines how backups on local shadow volumes are managed and retained.
Although Tivoli® Storage Manager policy determines how Data Protection for Microsoft Exchange backups are managed on Tivoli Storage Manager storage, backup retention on local shadow volumes is determined by version and time-based policies. Ensure that sufficient local storage space is available on local shadow volumes for a VSS backup. In addition, verify that enough available storage space is assigned to the volumes to accommodate your backup operations. The shadow copy volume that is the storage destination of a snapshot must have sufficient space for the snapshot.
Environment and storage resources also affect how many backup versions are maintained on local shadow volumes. The amount of space that is required depends on the VSS provider that you use.