This topic describes how to enable PolarDB for PostgreSQL to automatically create backups at specified intervals or manually create backups to prevent data loss in a timely manner. PolarDB for PostgreSQL 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

Table 1. Pricing
Region Level-1 backup Level-2 backup Log backup
Mainland China $0.000464 USD per GB-hour $0.0000325 USD per GB-hour $0.0000325 USD per GB-hour
China (Hong Kong) and regions outside China $0.000650 USD per GB-hour $0.0000455 USD per GB-hour $0.0000455 USD per GB-hour

Billing methods

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 PolarDB console.

Storage fee per hour = (Total physical storage of level-1 backups - Free quota) × Unit price per hour
  • You are not charged 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.
  • The following figure shows you how to view Total Physical Storage of Level-1 Backups in the console.Total Physical Storage of Level-1 Backups
    Note The physical storage of level-1 backups of a PolarDB cluster is the sum of the dedicated physical storage consumed by all level-1 backups, as shown in part ①. This metric 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 calculated only once in the bill. For more information, see FAQ.

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 USD 0.0928.

The fee is calculated based on the following formula: [700 GB - (1,000 GB × 50%)] × USD 0.000464/GB/hour = USD 0.0928/hour.

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 USD 0.0325.

The fee is calculated based on the following formula: 1,000 GB × USD 0.0000325/GB/hour = USD 0.0325/hour.

Log backup 100GB Storage fee per hour = (Total physical storage of log backups - 100 GB) × Unit price per hour

For example, if the total physical storage of log backups is 1,000 GB, the storage fee per hour is USD 0.02925.

The fee is calculated based on the following formula: (1,000 GB - 100 GB) × USD 0.0000325/GB/hour = USD 0.02925/hour.

Backup methods

Backup method Description
Automatic system backup
  • 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 the automatic backup feature.
  • 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 based on your business requirements. 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.
Backup method Description
Automatic system backup Standard backup
  • 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 the automatic backup feature.
  • Automatic backup files cannot be deleted.
Note To prevent data loss, automatic backup must be performed at least twice a week.
Enhanced backup PolarDB allows you to create backups at intervals of 2, 3, or 4 hours for the data that is generated within the last 24 hours.

After you enable enhanced backup, all backups are retained for 24 hours. Backups are automatically deleted when the retention period expires. However, the system permanently retains the first backup that is created after 00:00 every day.

For example, if you specify a backup frequency of every 4 hours at 08:00 on March 1, the system automatically creates the first backup within 4 hours from 08:00 to 12:00 on March 1. Then, the system continues to create a backup at an interval of 4 hours.

If the current time is 16:00 on March 4, the system retains the following backups:
  • The backups created within the last 24 hours (from 16:00 on March 3 to 16:00 on March 4).
  • The backups created between 00:00 and 4:00 on March 3.
  • The backups created between 00:00 and 4:00 on March 2.
  • The backups created between 08:00 and 12:00 on March 1.
1
Then, after 4 hours or at 20:00 on March 4, the system retains the following backups:
  • The backups created within the last 24 hours from 20:00 on March 3 to 20:00 on March 4.
  • The backups created between 00:00 and 4:00 on March 3.
  • The backups created between 00:00 and 4:00 on March 2.
  • The backups created between 08:00 and 12:00 on March 1.
2
Manual backup
  • You can manually back up data based on your business requirements. 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 the automatic backup feature

  1. Log on to the PolarDB console.
  2. In the upper-left corner of the console, select the region where the cluster that you want to manage is deployed.
  3. Find the cluster that you want to manage and click the cluster ID.
  4. In the left-side navigation pane, choose Settings and Management > Backup and Restore.
  5. Click the Backup Settings tab.
  6. Click Edit on the right of Backup Settings. In the dialog box that appears, set the following parameters.
    Type Parameter Description
    Back up Data Backup Frequency You can select Standard Backup or Enhanced Backup.
    • Standard Backup: Specify the backup cycle and start time of automatic backup.
      Note To prevent data loss, automatic backup must be performed at least twice a week.
    • Enhanced Backup: Set the backup frequency. You can select Last 24 Hours, Every 2 Hours, Last 24 Hours, Every 3 Hours, or Last 24 Hours, Every 4 Hours.
    Data Backup Retention Period Specify the retention period for level-1 backups and level-2 backups.
    • Level-1 Backup: Set the retention period for level-1 backups.
      Note Level-1 backups are retained for 3 to 14 days.
    • Level-2 Backup: Enable or disable the level-2 backup feature.
      Note By default, the level-2 backup feature is disabled.
    Log Backup Log Backups Retained For Specify the retention period for log backups.
    Note
    • Log backups are retained for 3 to 7,300 days.
    • If you need to permanently retain log backups, you can select Retained Before Cluster Is Deleted. The retention period parameter becomes unavailable after you select this option.
    General When Cluster is Deleted 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 most recent backup after you delete a cluster.
    • Immediately Delete All Backups: does not retain backups 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 the 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 that you want to manage is deployed.
  3. Find the cluster that you want to manage and click the cluster ID.
  4. On the Backups tab, click Create Backup.
  5. In the Create Backup message, click OK.
    Note You can create up to three backups for a cluster.

Restore data

For more information, see Restore data.

Related API operation

API Description
CreateBackup Creates a full backup of a specified PolarDB cluster.
DescribeBackups Queries the backup information about a specified PolarDB cluster.
DeleteBackup Deletes the backups of a specified PolarDB cluster.
DescribeBackupPolicy Queries the automatic backup policy of a specified PolarDB cluster.
ModifyBackupPolicy Modifies the automatic backup policy of a specified PolarDB cluster.