HP B6960-96035 manual Restore and synthetic backup, Synthetic backup and media space consumption

Figure 73 Virtual full backup

Figure 73 on page 260 shows how a virtual full backup is created. With this type of backup, all the backups reside in a single file library that uses distributed file media format. The Restore Media Agent (RMA) reads the information about the full backup and the incremental backups, and generates the data for the virtual full backup. The generated data is sent to the Backup Media Agent (BMA), which creates the virtual full backup in the file library.

Synthetic backup and media space consumption

If synthetic backups are performed frequently, and the sources are kept, this typically means significant space consumption on the backup media. However, if virtual full backup is performed, the backup media space consumption is minimized.

With virtual full backup, the space consumption largely depends on the size of the backed up files. If the files are significantly larger than the block size used, virtual full backup achieves maximum savings of the space compared to normal synthetic backup. On the other hand, if the files are smaller than the block size, the savings are rather small.

Restore and synthetic backup

Restore from a synthetic full backup is equivalent to restore from a conventional full backup. The following figures present different situations, supposing you need to restore your data to the latest possible state. In all examples, a full backup and four incremental backups of the backup object exist. The difference is in the use of synthetic backup.

260 Synthetic backup