Back up data

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. 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.

Pricing

Billing methods

Backup methods

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. 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.
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