Corrupted block detected in backup with clean logs - can`t restore it

[smoking_man]

Hello guys,

I have a problem with backup with corrupted block on a 123 GB position (whole backup is 500 gb), and this corrupted fragment makes unpacking/restore of a whole backup impossible, although other blocks are fine.

I do not understand fully the situation, how blocks got corrupte cause when I scrutinize file with logs of created backup it is 100% fine (I attach them), without errors, and it should work fine, but it doesn’t. Sum of md5 is also correct.

While unpacking I got this kind of error:

root@DEDICATEDSERVERNAME:/var/lib/vz/dump# zstd -t /var/lib/vz/dump/vzdump-qemu-103-2025_01_26-02_00_06.vma.zst
_26-02_00_06.vma.zst : 123143 MB... 26-02_00_06.vma.zst : Decoding error (36) : Corrupted block detected

Can you please give some suggestions how to repair this, what could caused the problem?

As webpages and webmail of my clients are offline now, and situation is bad and getting worse, i would kindly appreciate fast response .

Greets
SmokingMan

 

[Chris]

Hi,

I do not understand fully the situation, how blocks got corrupte cause when I scrutinize file with logs of created backup it is 100% fine (I attach them), without errors, and it should work fine, but it doesn’t

creating a backup successfully does not give you the guarantee that it will restore, you should run regular restore tests.

Sum of md5 is also correct.

I assume you mean the md5sum of the compressed archive after downloading it to a local storage matched the one of the archive as stored on you initial backup storage. Or what do you mean by this?

root@DEDICATEDSERVERNAME:/var/lib/vz/dump# zstd -t /var/lib/vz/dump/vzdump-qemu-103-2025_01_26-02_00_06.vma.zst
_26-02_00_06.vma.zst : 123143 MB... 26-02_00_06.vma.zst : Decoding error (36) : Corrupted block detected

Can you please give some suggestions how to repair this, what could caused the problem?

It seems that this is a corruption on the zstd level, so restoring this might turn out to be impossible. Maybe you have another backup you can restore from?

Anyhow: You could check if there is a hardware issue which might be at fault, e.g. by trying to restore on a different PVE host or run a prolonged memory test. Some further things you can try are discussed in this thread https://forum.proxmox.com/threads/restore-backup-failure-zstd-decompression.74636/