Recovering Corrupted Backup

[tylergun]

Hello all,

I tried searching for this but couldn't find an answer, hopefully someone can help.

Lets say I'm backing up a 1 TB VMware VM with 5 disks. I've got a backup through Veeam, and through an error in the underlying storage, a part of the vbk file gets corrupted. Lets say this is a small error, only a few bytes are wrong, but enough that a CRC no longer validates and Veeam determines the backup to be corrupt.

It's possible only 1 of the 5 disks has any errors, and may just be in a random file, non-critical to the operation of the VM.
In this scenario, am I able to restore the VM, despite it being partially corrupt, and just dealing with what may missing or broken in the resulting VM? Or will Veeam prevent me from restoring from a partially corrupt backup.

Thanks.

[PetrM]

Hi Tyler and Welcome to Veeam R&D Forums!

Basically, restore job will be failed if a corrupted block is found. However, corruption errors can be divided into three main groups:
1. Backup file header
2. Backup metadata
3. Data (f.e. VM disks)

In theory, the issues related to 1 and 3 can be fixed by our support team but they need to analyze every specific case to make the conclusion whether it is possible to restore from a damaged file or not. For example, in case of data corruption, typically you encounter errors with decompression algorithms and such problems can be fixed by customized agents that restore corrupted blocks as if they were empty blocks. You can try to obtain such customized agents from the support team. In case 2, there is no way to recover from such a file as metadata snapshots play the role of backup file MFT, you can find more information in this KB.

Thanks!

[tylergun]

Hi Petr,

Thanks for the reply. That's good to know, and I'm not at all surprised that if the Backup metadata were corrupt there would be not much that could be done.
I'm surprised that if the file header was corrupted there is a chance it could be recoverable, but I guess some of that data may not be essential to the restore process.

In short, if we face this issue, there is a chance Veeam Support can help, and we should reach out if we have this issue in the future.

Thanks.

[PetrM]

Hi Tyler,

Your understanding is absolutely correct. Also, some issues related to data corruption could be sophisticated from troubleshooting perspective and you always have an option to escalate a support case if you feel that it's not on the right track.

Thanks!