Explanation of backup data size - Database Backup - Alibaba Cloud Documentation Center

This topic introduces the concept of backup data size in Database Backup (DBS).

Definition

Backup data size refers to the actual volume of the data that has been transmitted over the DBS server.

Common concepts

Database backup scenarios involve the following concepts: database disk space, data file size, backup data size, and storage data size.

Data amount	Description
Database disk space	The total space consumed by data files, logs, operating system files, and the available space of the operating system of the server where the database resides. Note For an ApsaraDB RDS instance, the storage space that you select when you purchase the instance is database disk space. For a database hosted on an Elastic Compute Service (ECS) instance, the collective storage space of the system and data disks that you select when you purchase the ECS instance is database disk space.
Data file size	The amount of disk space occupied by database data files on the server where the database resides. You can perform the following operations to view the data file size of a database: To view the data file size of an ApsaraDB RDS database: On the Instances page, find the instance that you want to view the data file size and click Manage in the Actions column. In the left-side navigation pane, click Monitoring and Alerts. By default, the Resource Monitoring item is selected on the Standard Monitoring tab. In the Disk Space line chart, move the pointer over the chart to view Data Usage. To view the data file size of a database hosted on a Linux server, go to the directory of the database files and run the `du -sh` command. To view the data file size of a database hosted on a Windows server, open the folder where the database files reside. Right-click the blank area and select Properties.
Backup data size	The amount of data backed up by using Database Backup (DBS). This size depends on a variety of factors such as the database type, backup mode, and backup granularity.
Storage data size	The volume of data stored in the storage system. This size depends on a variety of factors such as the backup data size, the storage format of backup data, and the compression algorithm.

The following space sizes are in descending order: database disk space > data file size > backup data size > storage data size.

You can reduce the backup data size by modifying configuration items provided by DBS, such as the backup granularity and backup cycle, to reduce the DBS cost. You can use the compact storage format, compression methods, and automatic dumping and cleaning policies provided by DBS to reduce the storage data size and in turn the Object Storage Service (OSS) cost.

References

You can reduce the backup data size or storage data size by modifying the backup objects, backup cycle, and backup compression configurations, or deleting the backup sets of a DBS backup schedule. For more information, see Manage a backup plan.
DBS allows you to retain minimal backup sets to prevent data from being unable to be restored due to accidental deletion of all backup sets. For more information, see Retain minimal backup sets.
For information about the billing of DBS, see Billing overview.
If a large amount of data needs to be stored during a backup, we recommend that you purchase subscription DBS storage plans to offset the storage fees. For more information, see Use storage plans. Storage plans are more cost-efficient than the pay-as-you-go billing method.