Problem with Backup question

I was doing the About practice test and I got this question:

You want to perform multiple backups of only those files that are modified since the last normal backup. You also want to ensure that the backed up files use minimum amount of media. In this case, you will take a:

a. Normal backup.

b. Differential backup.

c. Incremental backup.

d. Copy backup.

And the answer was C. But Incremental backup will only backup what has changed from the last backup.
And in my opinion the answer should be B, because Differential will backup what has changed from the last full backup.
So, which one is the right one?

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Comments

kalebksp

You're right. The key points of the question are "multiple backups" and "since the last normal backup." They chose incremental, but you couldn't make multiple backups, because it resets the archive bit and as you said it doesn't back up everything since the last normal backup.

TeKniques

Just reading the question I thought it was Incremental the whole time. Especially when the question said: "You also want to ensure that the backed up files use minimum amount of media."

Hence, Differential backups are bigger and require more media to back up.

gabrielbtoledo wrote:

But Incremental backup will only backup what has changed from the last backup.
And in my opinion the answer should be B, because Differential will backup what has changed from the last full backup.
So, which one is the right one?

So you're saying you can't restore on a Normal/Incremental backup schedule? It's possible to implement disaster recovery without using differential backups at all.

If the question stated something along the lines of 'reducing restore time' then Differential backup would be the way to go.

Just my thoughts.

gabrielbtoledo

I did think it was incremental till the part where it says:

since the last normal backup.

An Incremental will backup only the files that have changed from the last normal backup, and consecutively from others Incrementals.
So if the question is just an one time backup after the last normal backup, then the answer is correct (Incremental).

I'm not really sure if the answer given by About.com is correct, there is why I posted in here.

So you're saying you can't restore on a Normal/Incremental backup schedule? It's possible to implement disaster recovery without using differential backups at all.

Yes you can restore from a normal and incremental backups. It will take more jobs to get the recovery done, but it can be done.
And yes as well, you can only use normal and incremental backups, as I said above.

zenboy

.....only those files that are modified since the last normal backup. You also want to ensure that the backed up files use minimum amount of media.........

If I might add my 2 cents to this topic since I just studied on it. Although I haven't done any scenario question for this exams, I'm going to give my opinion on this (still new at this..hehe).
I would agree with Teknique because the question stated to "use minimum amount of media", but doesn't mention the time factor involve to restore; therefore, Incremental should be the answer. Differental would back up all the previous days after/besides the normal backup; therefore taking too much space on the media.

gabrielbtoledo

I guess you are right, but also because it says: "You want to perform multiple backups of only those files that are modified since the last normal backup.", which a Incremental and Differential will do. However, if a Incremental has been done already, then the backup will be based on the last Incremental.