When you create policy for your backups, consider these differences between backing up data to Tivoli® Storage Manager storage versus VSS disks.
A Tivoli Storage Manager backup operation stores the backed up data on Tivoli Storage Manager server storage. Although this type of backup typically takes longer to process than a backup to local shadow volumes, a Tivoli Storage Manager backup is necessary when long-term storage is needed. Saving Exchange data on tape for archival purposes is an example of needing long-term storage. Tivoli Storage Manager backups are also necessary for disaster recovery situations when the disks that are used for local backups are unavailable. By maintaining multiple backup copies on Tivoli Storage Manager server storage, a point-in-time copy is available if backups on the local shadow volumes become corrupted or deleted.
Backups to Tivoli Storage Manager server storage are dictated by time, not by versions.
Sufficient local storage space must be available on local shadow volumes for a VSS backup strategy to be successful. Ensure that there is enough available storage space that is assigned to the volumes to accommodate your Data Protection for Exchange backup operations. Environment and storage resources also impact how many backup versions are maintained on local shadow volumes (for VSS fast restore and VSS instant restore) and how many backup versions are maintained on Tivoli Storage Manager server (VSS restore and longer term storage). Create different sets of policies for backups to both local shadow volumes and to Tivoli Storage Manager server storage. If you are using a VSS provider other than the Windows VSS System Provider, make sure to review the documentation for that specific VSS provider.
Backups to local shadow volumes can be managed by both time and versions. However, because of a higher frequency of local snapshot creation, and VSS storage provisioning and space limitations, set up policy for local backups to be based on version limits. In addition, in DAG environments, all of the DAG members are to use the same local VSS policy.