ntbackup and restore from differential backups

[AussieGal]

Hello

I am having difficulty finding the most relevant newsgroup for my question
so if anyone knows a better newsgroup to ask it, please advise.

I performed a full backup on a folder. A file was changed and saved. I did
a differential backup. I changed and saved the file again and did another
differential backup. I did this once again.

Now, to test what happens when restoring data that has been backed up using
differential backups, I simply restored the file I had been changing and
saving from the last differential backup to a 'New file', not the original
location. I was expecting some kind of error message or incomplete file.
When I opened the restored file it was complete with all the info added in
all of the changes.

This confused me as I thought that to restore the file completely I would
need to first restore it using the full backup and then restore each of the
differential backups.

Why did the file get fully restored from using only the last differential
backup?

Thanks.

 

[Maurice N ~ MVP]

Hello,
Reply in-line.

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Maurice N
MVP Windows - Shell / User
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"AussieGal" wrote

Hello

I am having difficulty finding the most relevant newsgroup for my question
so if anyone knows a better newsgroup to ask it, please advise.

I performed a full backup on a folder. A file was changed and saved. I did
a differential backup. I changed and saved the file again and did another
differential backup. I did this once again.

Now, to test what happens when restoring data that has been backed up using
differential backups, I simply restored the file I had been changing and
saving from the last differential backup to a 'New file', not the original
location. I was expecting some kind of error message or incomplete file.
When I opened the restored file it was complete with all the info added in
all of the changes.

This confused me as I thought that to restore the file completely I would
need to first restore it using the full backup and then restore each of the
differential backups.

You need only restore the file from the very last "set" that contains it. A differential backup has all of the files that had changes & has them in their entirety.

 

[AussieGal]

I forgot to say that I first tried this exercise using incremental backups
and got the same result. I figured I must have gotten the incremental and
differential backups mixed up (in what they achieved).

AussieGal


"AussieGal" wrote in message
news:[email protected]...

 

[Maurice N ~ MVP]

Is it possible the file had no changes (updates) in between the backup dates?

 

[AussieGal]

Hello MauriceYes, the file was changed between each backup. I altered the file between
each differential and incremental backup.

First used one normal backup followed by three incremental backups.
Restored the entire file by just using the last incremental backup up. I
was expecting to see an error message or a file not properly restored but
there was no error message and the file restored to its last full state.

I thought I had misunderstood the difference between incremental and
differential backups so I redid the whole exercise but this time used
differential backups. When I restored the file using the last differential
backup I got no error message and the file was restored. So.... now I am
confused.

If one tries to restore a file from an incremental backup aren't you
supposed to use the normal backup plus each incremental backup up to the
date of the desired file state? I understand that even is using
differential backup to restore a file that you would need to use the last
normal backup plus one differential backup.

Do people usually get an error message if they try and restore using only an
incremental backup? Or is the restored file just not supposed to function
properly? It would seem logical to expect some kind of error to occur
wouldn't it?

Thanks

Aussiegal


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