Data backup feature | Enabled by default | Retention period | Description | How to view backup size |
Level-1 backup | Yes | 3 to 14 days | The level-1 backup feature creates snapshots by using the Redirect-on-Write (ROW) method. The snapshots are directly stored in the distributed storage system of the PolarDB cluster. The level-1 backup feature does not duplicate data. When a data block is modified, the system saves the original version of the data block to a snapshot and redirects the writes to a new data block. In this case, you can back up data within a few seconds regardless of the size of your database storage. PolarDB clusters use multi-threaded parallel processing and other technical innovations to enhance data backup and restoration and can restore data from a backup set to a new cluster within 10 minutes.
Note By default, the level-1 backup feature is enabled, and you cannot disable this feature. Level-1 backups can be retained for up to 30 days. If you want to use this feature, contact us for admission to the whitelist.
| The physical size of level-1 backups is shown in the following figure. Note Total Physical Size of Level-1 Backups (Snapshots) of a PolarDB cluster: the total physical storage space occupied by all level-1 backups (callout 1 in the figure). The data of a PolarDB cluster and multiple level-1 backups (snapshots) use the same physical data blocks. You are charged based on data blocks. For more information about data backup, see FAQ. |
Level-2 backup | No | | The level-2 backup feature compresses and then stores level-1 backups in on-premises storage. Level-2 backup is slower compared with level-1 backup. However, level-2 backup is more cost-effective than level-1 backup. If you enable this feature, expired level-1 backups are transferred to on-premises storage and stored as level-2 backups. The backups are transferred at a rate of approximately 150 MB/s. You can implement level-2 backup across different zones in the same region or across different regions. For more information, see Intra-region and cross-region backups.
Note If a level-1 backup expires before the previous level-1 backup is transferred to a level-2 backup, the level-1 backup is deleted and is not transferred to a level-2 backup. For example, a PolarDB cluster creates a level-1 backup at 01:00 every day and retains the backup for 24 hours. If the PolarDB cluster creates Level-1 Backup A at 01:00 on January 1 and creates Level-1 Backup B at 01:00 on January 2. Level-1 Backup A expires at 01:00 on January 2 and starts to be transferred to a level-2 backup. However, Level-1 Backup A stores a large amount of data, and the transfer task is not complete by 01:00 on January 3. In this case, Level-1 Backup B is deleted after it expires at 01:00 on January 3 and is not transferred to a level-2 backup. | The following figure shows the total size of level-2 backups. The total size of level-2 backups is the sum of the data sizes of all level-2 backups. |