Introduction to Backups

RDS supports automated and manual backups. You can periodically back up databases. If a database is faulty or data is damaged, you can restore the database using backups to ensure data reliability.

RDS uses sysbench to import data models and a certain amount of data. After data is backed up, the compression ratio is about 80%. The more duplicate data there is, the higher the compression ratio is.

Compression ratio = Space occupied by backup files/Space occupied by data files x 100%

How RDS Backs Up Data

Single-node instance
A single-node architecture, which is more cost-effective than mainstream primary/standby DB instances. After a backup is triggered, data is backed up from the primary instance and stored as a package on OBS. The backup does not take up storage space of the instance.
Primary/standby instance
An HA architecture. In a primary/standby pair, each instance has the same instance class. After a backup task is triggered, data is backed up from the standby instance (or from the primary instance only when there is a long primary/standby replication delay) and stored as a package on OBS. The backup does not take up storage space of the instance.

If a database or table in the primary instance is maliciously or mistakenly deleted, the database or table in the standby instance will also be deleted. In this case, you can only use backups to restore the deleted data.

Figure 1 How RDS backs up data

Billing

Backups are saved as packages in OBS buckets. Backups occupy backup space in OBS. If the free space RDS provides is used up, the additional space required will be billed. For details, see How Is RDS Backup Data Billed?

After CBR snapshot-based backup is enabled, the free backup space is unavailable. You are billed for database server backup vaults on a pay-per-use basis. For details, see How Is CBR Billed?

Deleting Backups

Manual backups and automated backups can be deleted in different ways:
- Manual backups can only be manually deleted.
- Automated backups cannot be manually deleted. To delete them, you can adjust the retention period specified in your automated backup policy. When the retention period expires, automated backups will be deleted.
Local binlogs
If the retention period is set to 0, the binlogs of your DB instance will be deleted once they are synchronized to the standby instance and read replicas and successfully backed up to OBS.

If the retention period is set to a value greater than 0, for example, 1 day, the binlogs will be retained for one day after they are synchronized to the standby instance and read replicas from the primary instance and successfully backed up to OBS. After the retention period expires, the binlogs will be automatically deleted.