Automated Delta Pool Space Management

The set of operations by which Recovery Appliance manages backups is called automated delta pool space management. Specifically, space management involves the following automated tasks:

Deleting backups (both in a Recovery Appliance storage location and on tape) that are obsolete or expired based on the disk recovery window goal and SBT retention policy

Recovery Appliance periodically determines that some backups no longer need to be stored on disk, so their disk space can be reclaimed. When the Recovery Appliance determines that some backups residing in the delta pools are obsolete, the individual blocks that compose those backups are typically located in physical files alongside non-obsolete blocks. Recovery Appliance rewrites these physical files so that the delta pools can reclaim the space occupied by the obsolete blocks.
Reorganizing the delta pools periodically to improve performance of restore operations

The automatic tracking and reorganizing of the delta pools is called delta pool optimization. As old blocks are deleted and new incremental backups arrive for updated data files, the blocks in a backup can become less contiguous. This state can degrade the performance of restore operations. Recovery Appliance runs a background task that automatically reorganizes virtual full backup blocks to maintain contiguity, thus optimizing read access for restore operations.