This topic describes how to enable automatic backups at specified intervals or manually create backups for PolarDB for MySQL clusters to prevent data loss. PolarDB for MySQL allows you to retain backups of a cluster when you delete the cluster.

Backup types

Warning To disable the backup feature, submit a ticket. After you disable this feature, you must bear the risks that may arise. For example, data loss may occur due to user errors.
Backup type Description
Level-1 backup (data backup)

Level-1 backups are created based on Redirect-on-Write (ROW) snapshots. These snapshots are stored on 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 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. Compared with level-2 backups, it takes less time to create and restore level-1 backups. However, level-1 backups take up more storage space.

Level-1 backups can be retained for 7 to 14 days.

The following figure shows the total physical storage of level-1 backups.

The total physical storage of level-1 backups
Note PolarDB clusters are backed up and restored by using multi-threaded parallel processing. This improves efficiency. A level-1 backup (snapshot) can be restored or cloned at a rate of 1 TB every 40 minutes.
Level-2 backup (data backup) Level-2 backups are level-1 backups that are compressed and then stored in local 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.

Note
  • By default, the level-2 backup feature is disabled.
  • If you enable this feature, expired level-1 backups will be transferred to a local storage medium and stored as level-2 backups. The backups are transferred at a rate of approximately 150 MB/s.
  • If the current backup transfer task is not completed at the specified time, the system continues the ongoing backup transfer and skips the other transfer tasks. For example, the system creates backups at 01:00 (UTC+8) every day. Level-1 Backup A expires at 01:00 (UTC+8) and is transferred to a level-2 backup. However, Level-1 Backup A stores a large amount of data and the transfer task is not completed after 01:00 (UTC+8) the next day. Then, Level-1 Backup B scheduled for transfer is deleted at 01:00 (UTC+8) the next day when it expires.
Log backup

The log backup feature creates backups by updating Redo logs to Object Storage Service (OSS) in parallel. Based on a full data backup (snapshot) and Redo logs, you can perform point-in-time recovery (PITR) for a PolarDB cluster. Log backups can avoid data loss caused by user errors.

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 perform a PITR, you must first consider the amount of time that is required to query Redo logs. Redo logs are queried at a rate of 1 GB every 20 seconds to 1 GB every 70 seconds. The total restoration duration is the sum of the snapshot restoration time and the Redo logs query time.

Pricing

The backup and restoration features of PolarBD are free of charge. Only storage fees are charged. Fees are calculated based on the storage consumed by backups (data and logs) and the retention period of these backups.

Note

Alibaba Cloud has started to charge for the backup feature of PolarBD at 10:00 (UTC+8) on June 10, 2020. For more information, see [Notice] Alibaba Cloud begins charging for backups.

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
China (Hong Kong) and regions outside China USD 0.000650/GB/hour USD 0.0000455/GB/hour USD 0.0000455/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 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.
  • You can view the Total Physical Storage of Level-1 Backups on the location shown in the following picture.The total physical storage of level-1 backups
    Note The Total Physical Storage of Level-1 Backups refers to the sum of dedicated physical space consumed by all level-1 backups(that is the part ① shown as above picture), rather than the sum of the logical data size(that is the part ② shown as above picture). The data of the PolarDB cluster and multiple level-1 backups (snapshots) can be stored in the same physical block, which will only be calculated once in the bill. For more infomation about backups, see Backup FAQ.

For example, if the total physical storage of level-1 backups is 700 GB and database storage usage is 1,000 GB, then 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 = 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 USD 0.0325.

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

Log backup 100 GB 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 = 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 an automatic backup policy.
  • 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. On the top of the page, select the region where the target cluster is located.
  3. Find the target cluster and click the cluster ID to go to the Overview page.
  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
    Snapshot Backup The default value Snapshot Backup is used and cannot be changed.
    Backup Cycle: Specify the backup cycle.
    Note To prevent data loss, automatic backup must be performed at least twice a week.
    Start Time: Specify the start time for automatic backup.
    Level-1 Backups Retained For Specify the retention period for level-1 backups.
    Note Level-1 backups can be retained for 7 to 14 days.
    Level-2 Backup Enable or disable the level-2 backup feature.
    Note By default, level-2 backup is disabled.
    Log Backups Retained For: Specify 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: Specify 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 Specify the backup retention policy that applies when you delete a cluster.
    • Retain All Backups Permanently: retains all backups after you delete a cluster.
    • Retain Last Automatic Backup Permanently: retains the latest backup after you delete a cluster.
    • Delete All Backups Immediately: does not retain any backup after you delete a cluster.
    Note
    • If you choose the Retain All Backups Permanently or Retain Last Automatic Backup Permanently 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. On the top of the page, select the region where the target cluster is located.
  3. Find the target cluster and click the cluster ID to go to the Overview page.
  4. In the left-side navigation pane, choose Settings and Management > Backup and Restore.
  5. On the Backups tab, click Create Backup.
    Create a backup-cn
  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

  • Does the total physical storage of level-1 backups equal the sum of all backups?
    The total physical storage of level-1 backups does not equal the sum of all backups. The total physical storage of level-1 backups is displayed in the ① section, as shown in the following figure.The total physical storage of level-1 backups
  • Why is the total physical storage of level-1 backups smaller than the size of a single backup?

    Level-1 backups in Apsara PolarDB are measured by using two methods: the physical storage of all backups and the logical storage of each backup. Apsara PolarDB uses snapshot chains to store level-1 backups. Each data block is replicated only once. Therefore, the physical storage of all level-1 backups is smaller than the total logical storage of all level-1 backups, or sometimes even smaller than the logical storage of a single backup.

  • How are backups in Apsara PolarDB backup billed?

    Storage fees are charged for level-1 backups, level-2 backups, and log backups. By default, level-1 backup and log backup are enabled, but level-2 backup is disabled. Alibaba Cloud also offers free storage for level-1 backups and log backups.

  • What is the billing method of level-1 backups?

    Storage fee per hour = (Total physical storage of level-1 backups - Database storage usage x 50%) x Unit price per hour. For example, the total physical storage of level-1 backups of an Apsara PolarDB cluster is 700 GB and the database storage usage is 1,000 GB. Then, the storage fee per hour is calculated as (700 GB - 500 GB) × USD 0.000464/GB = USD 0.0928.

  • Can I use a storage plan to deduct the storage fee?

    No, a storage plan can only be used to deduct storage fees incurred by the stored data. It is not applicable to backups.

Related operations

API Description
CreateBackup Creates a full snapshot 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.