Block-Level Backup

Block-level backup is a faster method to back up data because only the extents that contain data are backed up, rather than the entire files.

Block-level backups provide better performance over file system backups and disk image-based backups if the file system has a large number of small files by reducing the scan times. Also, when compared to file system incremental backups, block-level incremental backups run faster and back up less data if the file system has very large files. Block-level backups might not be useful when backing up a portion of files or folders on a volume.

By default, block-level backups are performed using native snaps, but they can be configured to function with hardware snap engines.

Performance Comparison

The following table compares performance metrics between traditional backups and block-level backups on Linux, using the Recursive Scan method with cataloging disabled. Elapsed times are used to compare non block-level backups with equivalent block-level and block-level incremental backups.

Large Number of Small Files

Number of files: 11 million

Backup Type Scan Time Backup Time
Block-Level Backup 00:00:07 02:31:48
Traditional Backup 02:52:12 20:20:45
Image-Level Backup 00:05:37 04:28:33*
*Backup time includes metadata collection time.

Large Files

Average file size: 400 MB

Backup Type Scan Time Backup Time
Block-Level Backup (Full Backup) 00:00:15 00:46:05
Traditional Backup (Full Backup) 00:00:06 01:32:38
Image-Level Backup (Full Backup) 00:00:29 01:46:42
Block-Level Backup (Incremental Backup) 00:00:09 00:13:45
Traditional Backup (Incremental Backup) 00:00:06 00:46:58
Image-Level Backup (Incremental Backup) 00:04:16 00:41:45

File-level Restores

The following is comparison of file-level restore performance metrics between block-level restores and image-level restores on Linux:

Number of Files Block-Level Image-Level
1K 00:01:02 00:01:31
11K 00:02:45 00:12:33
100K 00:11:16 02:03:57