This topic answers frequently asked questions about the backup feature of PolarDB for MySQL.
- Does the total physical storage of level-1 backups equal the sum of all backups?
The total physical storage of level-1 backups does not equal the sum of all backups. The total physical storage of level-1 backups is displayed in the ① section, as shown in the following figure.
- Why is the total physical storage of level-1 backups smaller than the size of a single
Level-1 backups in Apsara PolarDB are measured by using two methods: the physical storage of all backups and the logical storage of each backup. Apsara PolarDB uses snapshot chains to store level-1 backups. Each data block is replicated only once. Therefore, the physical storage of all level-1 backups is smaller than the total logical storage of all level-1 backups, or sometimes even smaller than the logical storage of a single backup.
- How are backups in Apsara PolarDB backup billed?
Storage fees are charged for level-1 backups, level-2 backups, and log backups. By default, level-1 backup and log backup are enabled, but level-2 backup is disabled. Alibaba Cloud also offers free storage for level-1 backups and log backups.
- What is the billing method of level-1 backups?
Storage fee per hour = (Total physical storage of level-1 backups - Database storage usage x 50%) x Unit price per hour. For example, the total physical storage of level-1 backups of an Apsara PolarDB cluster is 700 GB and the database storage usage is 1,000 GB. Then, the storage fee per hour is calculated as (700 GB - 500 GB) × USD 0.000464/GB = USD 0.0928.
- Can I use a storage plan to deduct the storage fee?
No, a storage plan can only be used to deduct storage fees incurred by the stored data. It is not applicable to backups.