The backup copy job constantly transforms the full backup file in the backup chain to meet retention policy settings. The transformation process, however, has a side effect. In the long run, the full backup file grows large and gets badly fragmented. The file data occurs to be written to non-contiguous clusters on disk, and operations of reading and writing data from and to the backup file slow down.
To resolve the fragmentation problem, you can instruct Veeam Backup & Replication to compact the full backup file periodically. During the file compact operation, Veeam Backup & Replication creates a new full backup file on the target repository: it copies existing VM data blocks from the old backup file, rearranges and stores them close to each other. As a result, the full backup file gets defragmented, its size reduces and the speed of reading and writing from and to the file increases.
To compact the full backup file periodically, you must enable the Defragment and compact full backup file option in the backup copy job settings and define the compact operation schedule. By default, the compact operation is performed on the last Saturday of every month. You can change the compact operation schedule and instruct Veeam Backup & Replication to perform it weekly or monthly on specific days.
Limitations for Full Backup File Compact
The full backup file compact has the following limitations:
- The Defragment and compact full backup file option can be enabled only for the simple retention policy scheme.
- The target backup repository must have enough space to store a file of the full backup size. During the compact process, Veeam Backup & Replication creates an auxiliary VBK file that exists on the backup repository until the end of the compact operation.
- If the full backup file contains data for a VM that has only one restore point and this restore point is older than 7 days, during the compact operation Veeam Backup & Replication will not copy data for such VM to the newly created full backup file. Veeam Backup & Replication will extract data for this VM from the full backup file and write this data to a separate backup file. The file will be displayed under the Backups > Disk (imported) node in the Home view. This mechanism helps remove data for VMs that are no longer processed with the backup copy job from the full backup file and reduce the size of the full backup file.
The mechanism works if the following conditions are met:
- The Remove deleted VMs data option is not enabled in the backup copy job settings.
- The Use per-VM backup files option is not enabled in the settings of the target backup repository.