Backup Disk Space Calculation
Exasol provides two types of backup - Full backup and Incremental backup, which can either be stored cluster internally or written directly to an external backup storage.
A typical backup cycle is:
- Sunday: full backup with 10 days retention time
- Monday to Saturday: incremental backup with 3 days retention time
Cluster internal backups will be stored redundantly to ensure, that even in case of a node failure, there is still a valid backup. If you use external storage, no backup redundancy is required.
Incremental backup can vary in size depending on the change rate of your database, which is hard to predict. To ensure that there is enough disk space in the cluster, we calculate with the maximum incremental backup size. Alternatively, you can calculate only with full backups (e.g., five backups) to have a comfortable headroom as for disk space in the cluster.
Calculate Backup Disk Space
Without internal backup on the cluster:
(full backup size * (no. of full backups + 1)) + (incremental backup size * no. of incremental backups)
With internal backup on the cluster:
[(full backup size * (no. of full backups + 1)) + (incremental backup size * no. of incremental backups)] * 2
Creating a new backup does not remove the old backup, and for some time there is an additional backup (latest backup + old backup), which requires space (number of full backups+1).
With the following inputs:
- Full backup count: 2
- Incremental backup count: 3
- Maximum incremental backup size: 100% of full backup
- Cluster internal backup: Yes
- Backup redundancy: 2
The final backup space calculation which also includes headroom of one extra backup to avoid incidents during backup creation.
|Overall data volume (net)||Full backup data size||Incremental backup data size||Backup space (without redundancy)||Backup disk space required with redundancy|
1200 GiB (compressed data + indexes / statistical & auditing data)
1200 GiB x 2
1200 GiB x 3
Full backup data size + Incremental backup data size
Backup space (without redundancy) x 2 (this is calculated because the backups in this example are cluster-internal)