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Verify after the backup operation?


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Hi.

 

Running Retrospect 6.1.126 on a G4 iMac with 10.4.5, backing up on DVD-R discs. The last backup took much longer than expected (many more changed files than expected), so I had to abort the verification (compare) part of the backup before it finished.

 

Is there any way to verify the last snapshot, comparing against hard drive contents?

In this case, it would be DVD-R discs 19 through 26. I know I can verify the discs are readable, but I don't need to verify discs 1 through 18 and that kind of verification doesn't compare against hard drive contents.

 

Regards

Lennart

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Hi Lennart,

 

Unfortunately there is not an option to run a post-backup verification against the source. The best thing you could do would be to run another backup which would compare your backup to your source volume, if any files don't match it will update with those files. Then you'll at least have the most recent version of all the files on that source.

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Lennart,

 

You can try for such an enhancement request, but it's not possible to do so for a live system because there will always be verification errors as files change. The standard thing that modern backup programs do to handle this situation is to calculate a polynomial checksum of each file as it is being backed up, and then to permit checksum verification. If the checksum verification of the file on the tape matches the checksum in the list of files backed up (or of the file still on the disk), then you know everything is OK. That's how BRU (Tolis Group) does it, and how Retrospect 7.5 (for Windows, which uses MD5) does it. Let us hope that this feature migrates to the Mac Retrospect version. Let us send chocolate and coffee to the Mac Retrospect programmers so that they keep working furiously.

 

If what you are asking for is to be able to repeat the backup verification pass at a later date, that might be possible but its utility is questionable (for the above reasons), and the effort is probably better spent implementing checksums. If you think that Retrospect is a CPU hog now, just wait until it starts computing MD5 checksums on the fly - the processing demands go up sharply. See the complaints in the Windows Retrospect forums.

 

Russ

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Quote:

You can try for such an enhancement request, but it's not possible to do so for a live system because there will always be verification errors as files change.

 


Hi.

 

Yes, I'm aware of a number of files that WILL change.

Despite that, it would be nice to be able to do a compare after the backup.

How do I file an enhancement request?

 

Regards

Lennart

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  • 1 month later...

I've been in this situation a couple of times - where the computer crashed during the verification of an extremely long backup, and I wanted to figure out how much of the backup is good.

 

Reading Foster's post - "The best thing you could do would be to run another backup which would compare your backup to your source volume, if any files don't match it will update with those files" - this implies that a regular backup effectively checks whether what is has stored for the backup (on the DVD-R or whatever) is different from the source. Is that correct? And if so, how does it do that?

 

Thanks.

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Quote:

this implies that a regular backup effectively checks whether what is has stored for the backup (on the DVD-R or whatever) is different from the source. Is that correct? And if so, how does it do that?

 


No it's not (entirely) correct. Retrospect checks what it THINKS is stored, that is, has been written to the media without errors. Retrospect can't know if the verify failed or not. Anything that Retrospect doesn't consider written to the media gets backed up.

So if you suspect a bad media, you can co onto Configure->Backup Sets->Members and "Set Missing". Anything stored on that tape/CD/DVD will get backed up next time.

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RTFM?

The manual is over 200 pages and can be quite daunting. You have large chapters about features you never know if you need to use.

 

Another tip:

Tools->Verify. If you don't wan't to verify a tape/disc, just click on Options and then "Set Missing" (even if it isn't missing). I did this today, verifying DVDs 10-12 without spending time on 1-9, which I verified earlier.

Later, you must go to Configure->Backup Sets->Members and "Set Found".

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Quote:

Another tip:

Tools->Verify. If you don't wan't to verify a tape/disc, just click on Options and then "Set Missing" (even if it isn't missing). I did this today, verifying DVDs 10-12 without spending time on 1-9, which I verified earlier.

Later, you must go to Configure->Backup Sets->Members and "Set Found".

 

 


Watch out with this - there are a number of posts in the forums here that once a 6.0 Catalog is marked "Set Missing" with 6.1, there is no way to get the missing set back because the Set is not writable, and 6.1 has made the catalog unreadable by 6.0 (seems like a bit of a design flaw, here). But should be fine if it's a 6.1 catalog.

 

Russ

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  • 3 months later...

I don't see this feature (post backup compare against source) on the Windows 7.5 version either. I consider this sort of feature a must for any good PC backup program. Retrospect seems to have all the stuff to add this feature relativley easily and I would like to vote YES for this as well. While files do change on a live system, some files should NOT change in many cases, or if they do, an admin might want to know about it via an on-the-spot compare. I'm surprised this feature isn't already in the product.

 

Regards,

Tom

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