Backup Suddenly Failing

JSylvia007

Howdy all! I have a backup configuration that's been working fine for years. It's for some non-critical VMs, but recently, one of the VMs mysteriously started failing.

Since it's not critical, I just sad 'screw it', and deleted the backup and recreated the configuration. This completely new backup is still failing, and only on that one problem VM.

Error: stream has ended with not enough data (actual: 397, expected: 2097152)

Error: ENOENT: no such file or directory, stat '/opt/xo/mounts/9f2e49f9-4e87-444a-aa68-4cbf73f28e6d/xo-vm-backups/afe4bee2-745d-da4a-0016-c74751856556/vdis/7fc5396a-5383-4dab-91fe-6758eb8b7474/530abab7-9ea9-43d4-be6e-acb3fbf67065/20260323T124158Z.alias.vhd'

I re-ran it, and got some more info, but that could just be that the initial backup failed in this new backup configuration...

ADMIN-VM02 (xcpng01) 
Clean VM directory 
VHD check error
path
"/xo-vm-backups/afe4bee2-745d-da4a-0016-c74751856556/vdis/e57785aa-f99d-4f67-b951-5c6ac5fef518/530abab7-9ea9-43d4-be6e-acb3fbf67065/20260313T020007Z.alias.vhd"
error
{"generatedMessage":false,"code":"ERR_ASSERTION","actual":false,"expected":true,"operator":"==","diff":"simple"}

orphan merge state
mergeStatePath
"/xo-vm-backups/afe4bee2-745d-da4a-0016-c74751856556/vdis/e57785aa-f99d-4f67-b951-5c6ac5fef518/530abab7-9ea9-43d4-be6e-acb3fbf67065/.20260313T020007Z.alias.vhd.merge.json"
missingVhdPath
"/xo-vm-backups/afe4bee2-745d-da4a-0016-c74751856556/vdis/e57785aa-f99d-4f67-b951-5c6ac5fef518/530abab7-9ea9-43d4-be6e-acb3fbf67065/20260313T020007Z.alias.vhd"

missing target of alias
alias
"/xo-vm-backups/afe4bee2-745d-da4a-0016-c74751856556/vdis/e57785aa-f99d-4f67-b951-5c6ac5fef518/530abab7-9ea9-43d4-be6e-acb3fbf67065/20260313T020007Z.alias.vhd"

Start: 2026-03-23 17:26
End: 2026-03-23 17:26

Any idea what's going on here?

olivierlambert

Hi,

We need more details, because otherwise it's really hard to answer. Are you on XO source or XOA? Which commit/release?

JSylvia007

@olivierlambert - It's XO from sources. The about page says:

Xen Orchestra, commit d1736
Master, commit f2b19

What's weird is that I have 6 other backups, all configured the same way, and all work perfectly fine. There's even another VM in that same backup, and that one works fine too.

olivierlambert

First thing to do is to upgrade on latest commit available, because we can't know if it's a bug that could have been fixed before.

florent

@JSylvia007 this means that one of the task coalescing on of the older backups failed .

we are working on making it more observable, because for now it is a very opaque process. Even if the failure are rare, they can happen

I would advise you to check the toggle " merge synchronously" in the backup job if your backup window allow it. At least you will have an error message earlier

JSylvia007

@olivierlambert - You beat me to it. I did just that. I'm at the latest commit and just reran the backups. This is the ONLY VM that fails out of 6 VMs.

Failed with the exact same error. The files referenced are different, but the error related to the stream is the exact same.

The VM works fine. There's no indications that there's an issue with the virtual hard drives itself.

I've also tried with the VM running and powered off. Same issue.

It happens to be a Windows 10 VM. I do have another Windows VM that backup just fine (but it's a Windows Server VM).

They all backup to the exact same remote.

JSylvia007

@florent - It was on, I toggled it off, re-ran the backup, still failed.