This topic describes how to enable ApsaraDB PolarDB PostgreSQL-compatible edition to automatically create backups at specified intervals or manually create backups to prevent data loss. ApsaraDB PolarDB PostgreSQL-compatible edition also allows you to retain backups of a cluster when you delete the cluster.

Data backups

Data backups are divided into level-1 backups and level-2 backups by storage location.

The location where backup sets are stored Enabled by default? Retention period Characteristics How to view the size of a backup set
Level-1 backups Yes 3–14 days
  • Level-1 backups are created based on Redirect-on-Write (ROW) snapshots. These snapshots are stored in the distributed file system of PolarDB. 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 and 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.
  • The backup and restoration features of PolarDB clusters use multi-threading parallel processing and other innovative technologies. This allows you to restore data from a backup set (snapshot) to a new cluster within 10 minutes.
Warning By default, the level-1 backup feature is enabled. To disable the feature, you need to submit a ticket. We recommend that you keep the level-1 backup feature enabled if possible to reduce the risk of data loss. If the feature is disabled, data loss may occur, for example, due to user errors.
The following figure shows the total physical storage of level-1 backups. Total physical storage of level-1 backups
Note The total size of level-1 backups of a PolarDB cluster is the sum of the dedicated physical storage occupied by all level-1 backups, as shown in part ①. It is not the sum of the logical data sizes of all level-1 backups, as shown in part ②. The data of the PolarDB cluster and multiple level-1 backups (snapshots) can be stored in the same physical data block that is billed only once. For more information, see FAQ.
Level-2 backups No
  • 30–7,300 days
  • Enable the Retained Before Cluster Is Deleted feature to save level-2 backups permanently.
  • Level-2 backups are level-1 backups that are compressed and then stored in on-premises storage. Level-2 backups are slower to restore than level-1 backups. However, level-2 backups are more cost-effective than level-1 backups.
  • If you enable this feature, expired level-1 backups will be transferred to on-premises storage and stored as level-2 backups. The backups are transferred at a rate of approximately 150 MB/s.
Note If a level-1 backup expires before the previous one 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 level-1 backups at 01:00 every day and retains the backups 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 completed 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. 2

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.

Table 1. Pricing
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
  • You can use level-1 backups for free if the physical storage of the level-1 backups does not exceed the free quota.
  • For more information about the unit price per hour, see Table 1.
  • Section1 shows the total physical storage of level-1 backups.Total physical storage of level-1 backups

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
System backup (Auto)
  • By default, automatic backup is performed once a day. You can configure the start time and backup cycle for the automatic backup. For more information, see Configure automatic backup.
  • Automatic backup files cannot be deleted.
Note To prevent data loss, automatic backup must be performed at least twice a week.
Manual backup
  • You can manually back up data at any time. You can create up to three backups for a cluster. For more information, see Manually create a backup.
  • Manually created backup files can be deleted.

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 is deployed.
  3. Find the cluster and click the cluster ID.
  4. In the left-side navigation pane, choose Settings and Management > Backup and Restore.
  5. Click Backup Settings.
    Backup settings
  6. In the dialog box that appears, configure the following parameters.
    Backup settings-1
    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 Restore a released cluster.
  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 is deployed.
  3. Find the cluster and click the cluster ID.
  4. On the Backups tab, click Create Backup.
    Create a backup - cn
  5. 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.