# What Are Full Backup and Incremental Backup?

After an initial full backup, a server continues to be backed up incrementally by default.

- The initial full backup covers only the used capacity of a disk. If a 100 GB disk contains 40 GB data, the initial backup consumes 40 GB backup space.
- Subsequent incremental backup backs up data changed since the last backup. If 5 GB data changed since the last backup, only the 5 GB changed data will be backed up.

CBR allows you to use any backup, no matter it is a full or incremental one, to restore the full data of a resource. By virtue of this, manual or automatic deletion of a backup will not affect the restoration function.

Suppose server X has backups A, B, and C (in time sequence) and every backup involves data changes. If backup B is deleted, you can still use backup A or C to restore data.

In extreme cases, the size of a backup is the same as the disk size. The used capacity in a full backup and the changed capacity in an incremental backup are calculated based on the data block change in a disk, not by calculating the file change in the operating system. The size of a full backup cannot be evaluated based on the file capacity in the operating system, and the size of an incremental backup cannot be evaluated based on the file size change.

Parent topic: Concepts