The key difference between the two types of back-ups??? ---> im confused

[methodsboy]

what is the key difference between:
-incremental back-up
-differential back-up
Thank you.

[ell]

Complete (full) backup: Backup everything onto a separate medium

Differential backup: Consists of an initial full backup, then any changes made are backed up onto one separate medium (so you have stored one full backup, and another with any changes made after the full backup)

Incremental: Also consists of an initial full backup, then any changes made are backed up onto several media (so you would have a stored a full backup, plus each change made is stored on a separate medium. For example, after the initial full backup, you might make an incremental backup each month, March 2008, April 2008 etc.)

http://vcenotes.com/forum/index.php/topic,7745.msg96632.html#msg96632

Key difference - differential: one separate backup, incremental: more than one separate backup.

[methodsboy]

OH
so differential - each change made after the full back up is stored on ONE media
incremental - each change made after the full back up is stored on a separate media
is that right?

[ell]

Yeah. If you're using differential backup strategy, you have two backups: the initial full backup, and the differential backup where everything that is "different" from the full backup is saved.

Using an incremental backup strategy, you could have as many backups as you like. Think of an incremental backup as a differential backup split up into a lot of pieces that are usually organised (e.g. separate backups made each for January, February, March.. etc instead of having one big backup with all the monthly changes in it).

[methodsboy]

Yeah. If you're using differential backup strategy, you have two backups: the initial full backup, and the differential backup where everything that is "different" from the full backup is saved.

Using an incremental backup strategy, you could have as many backups as you like. Think of an incremental backup as a differential backup split up into a lot of pieces that are usually organised (e.g. separate backups made each for January, February, March.. etc instead of having one big backup with all the monthly changes in it).

Thanks ! i get it now

[TonyHem]

Another difference I was taught was that differentials backups everything from the last full back up.
EG: Full back on monday - and doing a differential every other day (tue/wed/thur/fri ) and then doing a differential on a friday still backs up everything since that monday.
and incremental would back up everything since the last back up - eg: back up on a friday, then doing an incremental on saturday backs up all the changes since that friday's backup.

Maybe thats wrong- im not too sure. My teachers had a little talk about that during the last SAC on IT:a last year, they ended up giving points to two different options.

[ell]

That's correct and it was what I was saying before, just not explicitly. Differential backups include everything changed (different) from the initial full backup, even if you have already backed it up previously.