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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.

Compared to file system backups and disk image-based backups, block-level backups reduce scan times when the file system has a large number of small files. 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 because block-level backups take a snapshot of the entire volume.

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

For more information on the benefits of using block-level backups, see Block-Level Backups.

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.

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Test data and system configuration details

Subclient content:  Random set of unique files of 30 KB, 50 KB, and 80 KB sizes
Machine CPU RAM Swap Operating System Version
Virtual machine - Linux client 1 2 GB 16 GB Red Hat Enterprise Linux 6.2 x86_64
Virtual machine - Linux MediaAgent 12 16 GB 16 GB Red Hat Enterprise Linux x86_64
Virtual machine - Windows CommServe 8 16 GB 16 GB Windows 2012 R2

Backups

         
Backup Type Scan Time Backup Time Throughput GB/hr Application Size Number of Files
Block-level backup (full) 00:00:23 13:39:41 79.77 GB/hr 1.05 TB 4,064,572
Traditional backup (full) 00:06:50 22:27:58 47.66 GB/hr 1.05 TB 4,064,572
Block-level backup (incremental) 00:00:33 02:14:29 79.4 GB/hr 177.2 GB 19,111 files sized 8 MB each added, 14,051 files sized 8 MB each removed
Traditional backup (incremental) 00:08:16 01:48:47 73 GB/hr 132.08 GB 19,111 files sized 8 MB each added, 14,051 files sized 8 MB each removed

Restores

Restore Type Volume Size Restore Time Number of Files
Volume-level restore from a full block-level backup 1.1 TB 13:49:51  
File-level restore from a full block-level backup 1.1 TB 39:03:04 4,068, 651
File-level restore from a full traditional backup 1.1 TB 46:00:00 4,068, 649