Backup and restoration

Data backup

Physical log backup

• Benefits

  The log backup feature allows you to create backups by uploading real-time redo logs to Object Storage Service (OSS) in parallel. The feature is enabled by default, and log backups are retained for 3 to 7,300 days. You can permanently save log backups by enabling the Permanently Retain Backups before Cluster Deletion feature.

  Note

  By default, the log backup feature is enabled, and you cannot disable this feature.

  Based on a full backup set and the log backups generated after the backup set is created, you can perform point-in-time recovery for a PolarDB cluster. This prevents data loss and ensures data security. If you perform PITR, you must consider the amount of time that is required to query redo logs, which is affected by the amount and workload of your business data. In most cases, redo logs are queried at a rate of 1 GB every 20 seconds to 180 seconds. The total restoration duration is the sum of the time required to restore backup sets and the time required to query redo logs.

• View backup size

  The following figure shows the total size of log backups.

  

Intra-region backup and cross-region backup

• Differences

  Backup type	Description	Enabled by default	Scenario	Benefits
  Intra-region backup	Backup files are stored across different zones in the same region.	Yes Note By default, this storage method is enabled when you enable level-2 backup.	Long-term archiving	Allows you to reduce costs by dumping data at a low backup frequency.
  Cross-region backup feature	Backup files are stored across regions.	Disabled. You must manually enable cross-region backup.	Geo-redundancy and MLPS level 3	Allows you to reduce recovery point objective (RPO). This backup storage method is suitable for private network environments that are encrypted and highly secure. You can reduce costs by dumping data at a low backup frequency.

  Note

  Low-frequency level-2 backup: The backup frequency of level-2 backup is lower than that of level-1 backup.

• Alibaba Cloud regions in which the cross-region backup feature is supported

  Source region	Destination region
  China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), China (Shenzhen), and China (Hong Kong).	China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), China (Shenzhen), and China (Hong Kong). Note Cross-region backup files are replicated to a region that is different from the source region.
  US (Virginia)	US (Silicon Valley)
  China East 1 Finance	China East 2 Finance and China South 1 Finance
  China East 2 Finance	China East 1 Finance and China South 1 Finance
  China South 1 Finance	China East 1 Finance and China East 2 Finance

Backup data protection

• Tamper-proofing:

  • Data backups of are classified by storage location: level-1 backups are snapshots in PolarDB distributed storage, and level-2 and log backups reside in OSS. Both support Write Once Read Many (WORM) to prevent tampering.

• Malicious or accidental deletion prevention:

  • Manual deletion: You can delete only , not .

  • Automatic deletion upon expiration: Automatic backups are deleted when the retention period expires and cannot be disabled. The minimum retention period in is 3 days (default: 7 days), with backups running at least twice a week. Therefore, automatic full backup and log backup data cannot be completely deleted.

Pricing

You can use the backup and restoration feature free of charge. However, backup files consume storage space. For information about the billing rules for the backup storage space, see .