Which of the following BEST describes the difference between differential and incremental backups?
A.
An incremental backup requires fewer tapes for restoration than a differential backup.
B.
A differential backup tape takes less time than an incremental backup tape.
C.
A differential backup requires fewer tapes for restoration than an incremental backup.
D.
An incremental backup tape costs less than a differential backup tape.
Incremental vs. differential backup: A comparison
Antony Adshead, UK bureau chief, storage Thursday 12 February 2009 05:00
In this discussion on incremental vs differential backup, we define the two terms using definitions that most people in the industry agree upon. There are complications in terminology, however, and we will look at those issues as well.
Differential backup
Differential backups copy those files that have been changed since the last full backup took place. So if a full backup was done on Day 1, Day 2’s differential will copy all of the files that have changed since Day 1’s backup copied everything. Day 3’s differential backup will also copy all of the files that have changed since Day 1’s full copy was made.
The key advantage of differential backups comes when data needs to be restored. Because a full backup was taken and the differentials copied everything that subsequently changed, only the full backup and the latest differential need to be restored.
The main disadvantage is that the size of the differential copy increases each time a backup is taken until the next full version is made, which can begin to impinge on backup window duration.
Incremental backup
Incremental backups copy all of the files that have changed since the last backup was made. They do this whether the last backup was a full one or an incremental copy. So if a full backup was done on Day 1, Day 2’s incremental will back up all of the files that have changed since Day 1. Likewise, Day 3’s incremental backup will only copy those files that have changed since Day 2’s incremental took place.
The main advantage to incremental backups is that fewer files are copied in the period between full backups, which means you will get a shorter backup window. The main disadvantage is that when you want to carry out a complete restore, the most recent full backup and all of the subsequent incremental copies must be restored. This can make the restore process a lengthier one than when using a full backup plus the most recent differential copies only.
The answer given, C, won’t apply if there are more than a couple of Incremental backups in between Full backups.
Edit, please.
The answer given, C, won’t apply if there are LESS than a couple of Incremental backups in between Full Backups.
if u make one full per week, and just incremental at other day, and the server fail on last day, before full backup, u will need the full backup, and all other daily incremental backup tape to restore. But if u use diferential, u will need just the full backup tape, and the last differential backup tape.
So C is good. (with just incremental backups, u will need minimum 2 tape. But with just diferential, u will need maximum 2 tape.)
A is wrong, coz u need all other incremental backup from last full or diferential backup.
B is wrong, coz differential backup take more time to backup, than incremental.
D bump