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How does Bvckup 2 deal with corrupt files

berger20 :

Oct 10, 2018

Hi all,

I found some corrupts on my backup drive and wondered what Bvckup would do if it came across such files.
I made a text file, synced it to the backup, closed Bvckup, then edited the file. I used a program to set the timestamps to what they were before I made the change.

When I started Bvckup and synced again, it copied the new version of the file. I'm not sure how good a simulation of a corrupt file that is, but it has worried me; how does Bvckup deal with corrupt files?

If a file is synced, but a few weeks later (untouched) it corrupts, will Bvckup overwrite the working version of the file with the corrupted one on from my source?

Alex Pankratov :

Oct 11, 2018

How do you expect the program to tell corruptions from intentional changes?

berger20 :

Oct 12, 2018

If I copied/edited a corrupted file, then I agree the system and Bvckup would see that as a change to data and copy that to my backup drive.
But I'm looking to prove if a file corrupts without appearing as a change (such as minor HW failure, power surge, drive decay etc) how Bvckup reacts to this.

A corruption wouldn't have any system/human touching it; it would just break at a rawer level. So the timestamps shouldn't change and the OS (Windows for me) shouldn't see it as a file that has been accessed or opened.

I have experience some corruptions in the past, and I brought Bvckup to allow me to have a recent backup of my drive to restore any broken files. If my new source drive had a section that corrupted, I'm hoping Bvckup doesn't copy this over to my backup drive ...otherwise Bvckup could spread corrupted data to my backup drives!

Alex Pankratov :

Oct 12, 2018

You are describing what's called "bitrot" and it *is* a problem with long-term storage. What I meant with my original reply is this:

Bvckup assumes that a file was modified if a triplet of (created time, last-modified time, file size) changes. That's it.

So if there is a bitrot at source, the file will not be re-backed up because its last-modified time remains the same. So in this case you are in clear.

BUT if in addition to bitrot, there are some other changes to the file, then the file *will* be backed up again, including the corrupted section, as the program has no way of telling apart corruption and intentional changes.

berger20 :

Oct 24, 2018

Brilliant thank you, now I have a name for it!
I'm finding it tends to be on old files I haven't edited/opened in a while, so now armed with Bvckup; it's even more likely I'll have an working copy of my files.

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