This topic provides answers to frequently asked questions (FAQs) about the backup and recovery features of PolarDB for PostgreSQL.
Backup FAQ
Q: Is the total size of level-1 backups (snapshots) the sum of all individual level-1 backups (snapshots)?
A: No, it is not. The total size of level-1 backups (snapshots) is the size indicated by ① in the following figure, not the sum of all individual backups (②).
Q: Why is the total size of level-1 backups smaller than a single backup?
A: Level-1 backups in PolarDB are measured by two capacity metrics: the logical size of each backup and the total physical size of all backups. PolarDB uses a snapshot chain mechanism for level-1 backups. The same data blocks are recorded only once. Therefore, the total physical size is smaller than the total logical size. In some cases, the total physical size can even be smaller than the logical size of a single backup.
Q: What are the fees for PolarDB backups?
A: Storage fees are charged for level-1 backups, level-2 backups, and log backups. Level-1 backups and log backups are enabled by default and include a free quota. Level-2 backups are disabled by default.
Q: How are the fees for level-1 backups calculated?
A: The hourly fee is calculated using the following formula: [Total size of level-1 backups - (Database storage usage × 50%)] × Hourly price. For example, in the Chinese mainland, if the total size of level-1 backups for a PolarDB database is 700 GB and the database storage usage is 1,000 GB, the hourly fee is [700 GB - 500 GB] × USD 0.000464 = USD 0.0928.
Q: Do manual backups support only level-1 backups?
A: Yes, it is.
Q: What is the retention period for manual backups?
A: The retention period for manual backup files is determined by the duration specified for Level-1 Backup in the Data Backup Retention section of the backup policy settings.
Q: How can I view the size of level-2 backups?
A: You can view the size of level-2 backups on the Backups tab in the console.
Recovery FAQ
Q: How can I recover data after accidental operations, such as deleting a table, database, or cluster, or modifying data incorrectly?
A: You can choose a recovery method based on your scenario. For more information about data recovery, see Full restoration method 1: Point-in-time restore and Full restoration method 2: Restore from a backup set (snapshot).
Q: Can I specify a custom name for the new table after recovery?
A: Yes, you can.
Q: Can I perform a point-in-time restore without a data backup?
A: No, you cannot. A point-in-time restore first restores a full data backup created before the specified point in time to the cluster. Then, it uses physical logs to incrementally restore data to that point in time.