When planning backup storage for Database Backup (DBS), four distinct size metrics describe the data at different layers of the system. Each metric is smaller than the one before it, and understanding why helps you estimate storage costs accurately.
How it works
The four metrics form a descending hierarchy:
Database disk space > Data file size > Backup data size > Storage data size
| Metric | What it measures | Why it's smaller than the previous |
|---|---|---|
| Database disk space | Total space on the server: data files, logs, operating system files, and free space | — (the largest measure; the baseline) |
| Data file size | Disk space occupied by database data files only | Operating system files, logs, and free disk space are excluded |
| Backup data size | Amount of data that DBS backs up | Depends on database type, backup mode, and backup granularity |
| Storage data size | Volume of data stored in the backup storage system | Depends on backup data size, storage format, and compression algorithm |
Database disk space
Database disk space is the total space consumed by data files, logs, operating system files, and the available free space on the server where the database resides.
How it maps to specific resource types:
ApsaraDB RDS instance: The storage space you select when purchasing the instance is the database disk space.
Database on an Elastic Compute Service (ECS) instance: The combined storage space of the system disk and data disk you select when purchasing the ECS instance is the database disk space.
Data file size
Data file size is the amount of disk space occupied by database data files on the server where the database resides.
View the data file size
For an ApsaraDB RDS database:
On the Instances page, find the instance and click Manage in the Actions column.
In the left-side navigation pane, click Monitoring and Alerts. The Resource Monitoring item is selected by default on the Standard Monitoring tab.
In the Disk Space line chart, hover over the chart to view Data Usage.
For a database on a Linux server:
Go to the directory of the database files and run:
du -shFor a database on a Windows server:
Open the folder where the database files reside, right-click a blank area, and select Properties.
Backup data size
Backup data size is the amount of data that DBS backs up. The exact size depends on the database type, backup mode, and backup granularity.
Storage data size
Storage data size is the volume of data stored in the backup storage system. The exact size depends on the backup data size, the storage format of the backup data, and the compression algorithm applied.