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Studying for Security+ with Darril Gibson's book he says that "A full backup is the easiest and quickest to restore"

Now I've been looking for another test exams and I found the MasterExam of the CompTIA Security+ All-in-one book. One question was A disadvantage of a full backup is? and the right answer was It takes the longest time to restore.

So either Darril or Mc Graw Hill's book is mistaken.

What do you think? Is a full backup the quickest or the longest on restoring?

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    You're not new here, so I'm gonna spare you the "read the FAQ" drill. Just because it was written in a security book doesn't make it fit for Security.SE. This question is clearly off-topic.
    – Adi
    Commented May 22, 2013 at 12:44

4 Answers 4

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The answer here I think depends on a slightly old-school approach to backups. If you have an initial full backup to tape and you then do incremental backups to separate tapes, the incrementals backup quickly, however if you need to restore you may need to go through several different tapes to find all the files that you want to bring back, hence the slow restore.

In contrast full backups are slow to do (you're backing up all the data not just some) but the restore is quicker because any file you want back will be on that tape (as there is only one)

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  • I hadn't thought about tapes :p Commented May 22, 2013 at 12:58
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I believe the difference here is due to contextual details. Imagine you have backed up only the users’ home directories or had an incremental that covered the data needed to be resorted on one system and the complete host server backup on another system. If the context of your recovery is a user or rouge program overwrote users' data then the home directory/incremental only recovery is indeed faster as there is less data to update. If on the other hand the entire system failed and needed to be recreated then the full backup would be faster as it would contain all and could be installed in one session vice multiple incremental overwrites.

Simply stated for disaster recovery a current full backup is the fastest route to recovery but of recovering recent user data or system updates an incremental could well be faster depending on the details of the loss and backup routine.

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Full backup takes longer than eg. incremental backup, which is again faster than differential backup. Depending on the size of what you need to backup, a full backup is obviously slower at bigger sizes, but if your backing up something small a full backup might be faster since it has "no logic". Same goes for restore.

Please see:
http://en.wikipedia.org/wiki/Full_backup

I found this on a webpage once:

Easy Way To Remembering ProPerties

Full = F
Differential = D
Incremental = I

B = Backup
R = Restore

1 = Fastest
2 = Faster
3 = Slowest

    B   R  
F   3   1  
D   2   2  
I   1   3   
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There is no difference in restoring the backup (since the amount which should be restored for a differential or a full backup is the same). Where they differ is the size when they are made. A full backup stores all files every time a backup process is started, whereas a differential backup only stores files which were altered.

When the backup is restored a differential backup will just have a reference to the file rather than the actual file.