This topic provides answers to some commonly asked questions (FAQ) about the backup feature of ApsaraDB PolarDB PostgreSQL-compatible edition.
- Is the total size of level-1 backups (snapshots) equal to the sum of the sizes of all the level-1 backups (snapshots)?
No, the total size of level-1 backups (snapshots) is not equal to the sum of the sizes of all the backups (snapshots). The total size of level-1 backups (snapshots) is displayed in the ① section, as shown in the following figure.
- Why is the total size of level-1 backups smaller than the sum of the sizes of all the backups?
The size of level-1 backups in PolarDB is measured in two forms: the logical size of each backup and the total physical size of all the backups. PolarDB uses snapshot chains to store level-1 backups. Only one record is generated for the same data blocks. Therefore, the total physical size of all the level-1 backups is smaller than the total logical size of all the level-1 backups. In some cases, the total physical size of all the level-1 backups is smaller than the logical size of a single backup.
- How am I billed for backups in PolarDB?
You are billed for the storage space of level-1 backups, level-2 backups, and log backups. By default, the level-1 backup and log backup features are enabled and you can use some storage space for free. By default, the level-2 backup feature is disabled.
- What is the billing method of level-1 backups?
The fee is calculated based on the following formula: Storage fee per hour = (Total size of level-1 backups - Used database storage space × 50%) × Price per hour. For example, assume that the total size of level-1 backups of a PolarDB database is 700 GB and the used database storage space is 1,000 GB. Then, the storage fee per hour is calculated based on the following formula:[700 GB - 500 GB] × USD 0.000464/GB = USD 0.0928.
- Can I use a storage plan to offset the storage fees of backups?
No, you cannot use a storage plan to offset the storage fees of backups. A storage plan can be used to offset only the storage fees of business data.
- Is level-1 backup the only backup type that can be manually created?
Yes, only level-1 backups can be manually created.
- How long is a manually created backup retained?
A manually created backup is retained until it is manually deleted or the cluster is released. If you set the backup policy to Permanently Retain All Backups, the backup is retained after you delete the cluster.
- How do I view the size of a level-2 backup?
You can view the size of a level-2 backup on the Backups tab in the console.