Incremental and differential backups

Crunchyhippo

Not that I'm the first to mention it, but what is the practical difference, as it would appear on a test, between incremental and differential backups? I know the one has a bit turned off while the other has a bit turned on, but this is never stated on any practice test questions that I've seen so far, so how do I tell the two apart?

bighornsheep

I think the key difference lies when you restore the backup.

With incremental, you will need to restore all the incremental backup in order to bring you back to point present whereas differential only requires the last backup.

ps. This is a Network+ topic.

ajs1976

bighornsheep wrote:

ps. This is a Network+ topic.

Backups are also covered in Security+. Usually more indepth because it starts to talk about DR and Business Continuity.

bighornsheep

ajs1976 wrote:

Usually more indepth because it starts to talk about DR and Business Continuity.

Very true, I suspected Sec+ might cover backups and restoration, it was reflex that backups until this point in my life automatically meant "networking".

to the OP, this maybe helpful to brush up the different types: http://www.techexams.net/technotes/networkplus/fault_disast.shtml

And of course, These are particularly useful!

sprkymrk

bighornsheep wrote:

With incremental, you will need to restore all the incremental backup in order to bring you back to point present whereas differential only requires the last backup

A little clarification, although I assume this is what you meant, with incremental, you need all the previous incremental backups and the last full backup to do a restore. With differential, you need the last differential and the last full backup to restore.

Differential - faster restore but slower backup. This backup does not clear the archive bit, which causes it to be backed up again the next time a differential/full backup is run. This is why a differential will continue to back up files that have already been backed up (since the last full backup).

A full backup will clear the bit, however a full backup does not care whether the bit was set or not, it backs up everything you told it to back up whether the bit is set or not.

Incremental - slower restore but faster backup. This type of backup clears the archive bit, so unless the file is modified by some other program/user, it will not get backed up again. However, this is also why you will need every incremental backup made since the last full backup in order to do a full restore.


Hopefully I didn't make any glaring errors in my above summary...

bighornsheep

sprkymrk wrote:

with incremental, you need all the previous incremental backups and the last full backup to do a restore. With differential, you need the last differential and the last full backup to restore.

Differential - faster restore but slower backup. This backup does not clear the archive bit, which causes it to be backed up again the next time a differential/full backup is run. This is why a differential will continue to back up files that have already been backed up (since the last full backup).

A full backup will clear the bit, however a full backup does not care whether the bit was set or not, it backs up everything you told it to back up whether the bit is set or not.

Incremental - slower restore but faster backup. This type of backup clears the archive bit, so unless the file is modified by some other program/user, it will not get backed up again. However, this is also why you will need every incremental backup made since the last full backup in order to do a full restore.

Yes..yes...

I know we can all sometimes count on Mark to keep watch for my unclear statements