Back up data

Backup types

Backup type	Description
Level-1 backup (data backup)	Level-1 backups are created based on Redirect-on-Write (ROW) snapshots. These snapshots are stored in a cluster that supports distributed storage. The system does not replicate data when it saves a data block to a snapshot. When a data block is modified, the system saves one of the previous versions of the data block to a snapshot. At the same time, the system creates a new data block that is redirected by the original data block. Therefore, you can create backups within a few seconds regardless of the size of your database storage. Only a small amount of time is required to create and restore level-1 backups. However, level-1 backups take up large storage space. PolarDB clusters are backed up and restored based on the multi-threading architecture. This improves the efficiency. It takes 40 minutes to restore or clone 1 TB of data based on backup sets (snapshots). A backup can be retained for seven to 14 days. By default, the level-1 backup feature is enabled to ensure data security. The following figure shows the total size of level-1 backups (snapshots). Warning To disable the level-1 backup feature, submit a ticket to contact Customer Services.For more information, see Submit a ticket. However, after you disable this feature, you must bear the risks that may arise. For example, data loss may occur due to user errors.
Level-2 backup (data backup)	Level-2 backups are level-1 backups that are compressed and then stored in on-premises storage media. Level-2 backups are slower to restore than level-1 backups. However, the costs incurred for level-2 backups are lower than that of level-1 backups. Level-2 backups can be retained for 30 to 7,300 days. You can also enable the Retained Before Cluster Is Deleted feature. By default, the level-2 backup feature is disabled. If you enable this feature, expired level-1 backups are transferred to on-premises storage media and stored as level-2 backups. The level-1 backups are transferred to level-2 backups at a rate of approximately 150 MB/s. 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, the system creates level-1 backups at 01:00 every day for PolarDB clusters and retains the level-1 backups for 24 hours. The system 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. Therefore, after Level-1 Backup B expires at 01:00 on January 3, Level-1 Backup B is deleted and is not transferred to a level-2 backup.
Log backup	The log backup feature creates backups by uploading real-time redo logs to Object Storage Service (OSS) in parallel. Based on a full backup (snapshot) and the redo logs generated after the backup is created, you can perform point-in-time recovery (PITR) for a PolarDB cluster. Log backups can prevent data loss caused by user errors and ensure the security of data in the recent period. Log backups can be retained for 7 to 7,300 days. You can also enable the Retained Before Cluster Is Deleted feature to store data permanently. Note If you want to restore data to a specific time point, you must include the time required to replay the redo log files. It takes about 20 to 70 seconds to replay 1 GB of redo log data. The total restoration time is the sum of the time required to restore data based on backup sets (snapshots) and the time required to replay the redo log files.

Pricing

The backup and restoration features of PolarDB are free of charge. Only storage fees are charged. Fees are calculated based on the storage space that is consumed by backup files and the amount of time for retaining the backup files. Backup files consist of data files and log files.

Billing method

Backup methods

Configure automatic backup

1. Log on to the PolarDB console.
2. In the upper-left corner of the console, select the region where the cluster resides.
3. Find the cluster, and then click the cluster ID.
4. In the left-side navigation pane, choose Settings and Management > Backup and Restore.
5. Click Backup Settings.
   
6. In the dialog box that appears, configure the following parameters.
   

   Parameter	Description
   Backup Method	The default value Snapshot Backup is used and cannot be changed.
   Backup Cycle	Specifies the backup cycle. Note To prevent data loss, automatic backup must be performed at least twice a week.
   Start Time	Specifies the start time for automatic backup.
   Level-1 Backups Retained For	Specifies the retention period for level-1 backups. Note Level-1 backups can be retained for 7 to 14 days.
   Level-2 Backup	Enables or disables the level-2 backup feature. Note By default, level-2 backup is disabled.
   Level-2 Backups Retained For	Specifies the retention period for level-2 backups. Note Level-2 backups can be retained for 30 to 7,300 days. To retain level-2 backups permanently, select Retained Before Cluster Is Deleted. The retention period parameter becomes unavailable after you select this option.
   Log Backups Retained For	Specifies the retention period for log backups. Note Log backups can be retained for 7 to 7,300 days. To retain log backups permanently, select Retained Before Cluster Is Deleted. The retention period parameter becomes unavailable after you select this option.
   When Cluster Is Deleted	Specifies the backup retention policy that applies when you delete a cluster. Permanently Retain All Backups: retains all backups after you delete a cluster. Permanently Retain Last Automatic Backup: retains the latest backup after you delete a cluster. Immediately Delete All Backups: does not retain any backup after you delete a cluster. Note If you select the Permanently Retain All Backups or Permanently Retain Last Automatic Backup policy, the system runs an automatic backup task to store all data when you delete a cluster. After you delete a cluster, level-1 backups are automatically transferred to level-2 backups. You can go to the Cluster Recycle page to view stored backups. For more information, see Cluster recycle bin.

7. After you configure backup settings, click OK.

Manually create a backup

1. Log on to the PolarDB console.
2. In the upper-left corner of the console, select the region where the cluster resides.
3. Find the cluster, and then click the cluster ID.
4. In the left-side navigation pane, choose Settings and Management > Backup and Restore.
5. On the Backups tab, click Create Backup.
   
6. In the Create Backup dialog box, click OK.
   Note You can create up to three backups for a cluster.

Restore data

For more information, see Restore data.

FAQ

Related API operations