Incremental Backup

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What is Incremental Backup?

An incremental backup stores all files that have changed since the last full, differential or incremental backup. The advantage of an incremental backup is that it takes the least time to complete. However, during a restore operation, each incremental backup must be processed, which could result in a lengthy restore job.

Description of the Incremental Backup Type

Incremental backup provides a faster method of backing up data than repeatedly running full backups. During an incremental backup only the files that have changed since the most recent backup are included. That is where it gets its name: each backup is an increment since the most recent backup.

The time it takes to execute the backup may be a fraction of the time it takes to perform a full backup. Backup4all uses the information recorded in its catalog file (".bkc") to determine whether a file has changed since the most recent backup.

The advantage of reduced backup duration comes with a price: increased restore duration. When restoring from incremental backup, you need the most recent full backup as well as every incremental backup you've made since the last full backup.

For example, if you did a full backup on Friday and incremental on Monday, Tuesday and Wednesday, and the PC crashes Thursday morning, you would need all four backup container files: Friday's full backup plus the incremental backup for Monday, Tuesday and Wednesday. By comparison, if you had done differential backup on Monday, Tuesday and Wednesday, then to restore on Thursday morning you'd have needed Friday's full backup plus Wednesday's differential backup.

Advantages

•	Backing up is the fastest

•	It uses the least storage space

Disadvantages

•	Restore is the slowest

Incremental Backup Type in Backup4all

Backup4all supports incremental backup type and offers a solution for the slow restore issue.

To keep the number of stored backups to a reasonable number and reduce the size of the backups, Backup4all provides three options: Limit the number of file versions, Limit maximum number of stored backups to and Merge stored backup to maintain the maximum limit. These options will perform an internal merge to keep the number of stored backups under the selected limit.

The following options can be used to trigger the creation of a new full backup:

•	Automatically make full backup when all increments exceed ... % of full backup size (default is 50%, not checked)

•	Automatically make full backup when all increments exceed ... (default is 1 Mbyte, not checked)

The system calculates the file sizes for the incremental and if the selected condition is met, it performs a full backup.