A differential backup system backs up the changes made to a system between the initial backup and the current backup. Unlike an incremental backup system, wherein only the newest changes from the previous increment are recorded, the differential system backs up everything that has changed from the initial backup on each subsequent backup. One way to visualize this is to think of incremental backup data sets, where A is the initial backup, as A + B + C + D, whereas differential backups are A + B + BC + BCD.
While differential backups require more storage space, they make up for that in speed of restoration as you only need the original backup (the A in our example) plus the most recent differential (say, data set BCDE) to perform your restoration.
- By Jason Fitzpatrick on 11/5/13