Full Backup:

For example: A company finds that their data hardly change on a daily basis and decides to perform a full copy (backup job) of their folders and files on a weekly basis. They decided to call this backup job as ‘Weekly Full’ and used a remote storage location as the backup destination. Also, they may want to have a back-storage of four weeks such as, Weekly 1 Full, Weekly 2 Full, Weekly 3 Full and Weekly 4 Full. Then on Week 5 they start again from Weekly 1 as to rotate their backup job over four weeks. With this strategy they can go back to weekly restores to a maximum of four weeks.

Incremental Backup: Only the files which have been modified or created on the day are backed up. This method is very fast and consumes little storage space; however, it is best to incorporate a regular full backup with this method!  The restore operation is more complex as all the backups have to be restored in the correct sequence. Some backup systems refer to this method as a daily backup. An incremental backup resets the archive bit.

For example: The company requirements have changed and now they have files that are updated on daily basis. It was decided that apart from the weekly full backups, a daily incremental backup is introduced. While the weekly full backups are performed on a Saturday, the daily incremental were labeled as follows: Inc Mon for Monday’s, Inc Tue for Tuesday’s, etc.

Differential Backup: Only the files which have been modified or created since the last full backup are backed up. This method uses the previous full backup as a reference point and any file that has changed or was created after that reference point is backed up. A daily differential backup does not reflect on any previous differential backups but only on previous full backups. So, Friday’s daily differential would be larger than Monday’s. However, the restore operation is faster and simpler than the incremental as only the latest differential and full backups are needed. A differential backup does not reset the archive bit.

For example: The company wanted to restore 3 files that were updated on Monday, Tuesday and Wednesday. The restore request was done on a Friday morning and hence, they had to search the 3 (Monday, Tuesday & Wednesday) incremental backups and perform a lengthy restore operation. As a result it was decided that the daily backups are changed to differentials and will be called Diff Mon, Diff Tues, etc. Then a restore operation for the same 3 files would only require the latest differential backup.