Backup locks out VM

[EddieA]

I'm not sure what started triggering this, as I've been running the same backup to the Tuxis server for over 4 months now.

Just over a week ago, I noticed that a VM (the only one backed up) was having issues where it was in a "stuck" state for some time and the kernel was reporting a number of tasks as: "blocked for more than 120 seconds" and then killing the task. collectd was reporting that it's plugins were taking around 3 minutes to respond. Any attempt to login, or otherwise try to connect to the VM was also failing. Checking back on the time that this was happening matched when the backup was taking place.

Disabling the backup seems to have stopped this.

Any ides on what might have triggered this to start happening and how do I stop the backup from freezing the VM.

Cheers.

 

[UdoB]

May be this: https://forum.proxmox.com/threads/the-virtual-machine-slows-down-during-backup.110055/post-473731

In my understanding the effective write-speed from inside a VM is limited to the write-speed of the backup destination. While it feels as if short writes get buffered (if "sync" is not forced), larger writes are problematic...

Best regards
PS: there is a more detailed explanation somewhere in this forum...

 

[EddieA]

This wasn't a slow-down. It was a hard stop.

And why suddenly. I never noticed anything over the first 4 months of daily backups.

Cheers.

 

[UdoB]

Is there any information in the backup task log? (your VM --> Task History --> that Backup)

 

[EddieA]

Nothing that might show what's going on. And unfortunately those logs aren't timestamped, so you can't see where any hold-up might have happened.

Cheers.