This topic describes how to enable PolarDB for PostgreSQL to automatically create backups at specified intervals or manually create backups to prevent data loss. PolarDB for PostgreSQL also allows you to retain backups of a cluster when you delete the cluster.
Backup types
Backup type | Description |
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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.
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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.
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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.
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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.
Region | Level-1 backup | Level-2 backup | Log backup |
---|---|---|---|
Mainland China | USD 0.000464/GB/hour | USD 0.0000325/GB/hour | USD 0.0000325/GB/hour |
Hong Kong (China) and regions outside China | USD 0.000650/GB/hour | USD 0.0000455/GB/hour | USD 0.0000455/GB/hour |
Billing method
Backup type | Free quota | Billing method |
---|---|---|
Level-1 backup | Database storage usage × 50%
You can view the database storage usage of a cluster on the Overview page of the cluster in the console. |
Storage fee per hour = (Total physical storage of level-1 backups - Free quota) ×
Unit price per hour
For example, if the total physical storage of level-1 backups is 700 GB and the database storage usage is 1,000 GB, the storage fee per hour is CNY 0.6. The fee is calculated based on the following formula: [700 GB - (1,000 GB × 50%)] × USD 0.000464/GB = USD 0.0928. |
Level-2 backup | None | Storage fee per hour = Total physical storage of level-2 backups × Unit price per
hour
For example, if the total physical storage of level-2 backups is 1,000 GB, the storage fee per hour is CNY 0.21. The fee is calculated based on the following formula: 1,000 GB × USD 0.0000325/GB = USD 0.0325. |
Log backup | 100GB | Storage fee per hour = (Total physical storage of log backups - 100 GB) × Unit price
per hour
For example, if the total size of log backups is 1,000 GB, the storage fee per hour is CNY 0.189. The fee is calculated based on the following formula: (1,000 GB - 100 GB) × USD 0.0000325 = USD 0.02925. |
Backup methods
Backup method | Description |
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System backup (Auto) |
Note To prevent data loss, automatic backup must be performed at least twice a week.
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Manual backup |
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Configure automatic backup
Manually create a backup
Restore data
For more information, see Restore data.
FAQ
Related API operations
API | Description |
---|---|
CreateBackup | Creates a full snapshot backup for a specified PolarDB cluster. |
DescribeBackups | Queries the backup information of a specified PolarDB cluster. |
DeleteBackup | Deletes the backups of a PolarDB cluster. |
DescribeBackupPolicy | Queries the automatic backup policy of a specified PolarDB cluster. |
ModifyBackupPolicy | Modifies the automatic backup policy of a specified PolarDB cluster. |