Background
One of your VMs might just stop working. When you look at the icon in the Proxmox explorer you see a yellow triangle and when you hover over the yellow triangle, you see “io-error”. No other visible clues are present in the UI. When you go a console you may see the VMs output but it seems like the console is frozen. All other VMs are working fine.
This may occur because you’ve overprovisioned LVM disks.
To find problem events in Proxmox use the Linux tool journalctl. For example:
journalctl | grep -i "warning"
If your Journal is extremely large, in other words months or years of logs, you might want to vacuum it first:
journalctl --vacuum-time=8d
Now look for warnings again.
If there is an overprovisioning issue, you will see events similar to the following:
Nov 27 18:06:19 hostname kernel: device-mapper: thin: 253:8: switching pool to out-of-data-space (queue IO) mode Nov 27 18:06:28 hostname lvm[760]: WARNING: Thin pool pve-data-tpool data is now 100.00% full. Nov 27 18:07:21 hostname kernel: device-mapper: thin: 253:8: switching pool to out-of-data-space (error IO) mode
The solution is to free up disk space on the full volume.
Here are two possibilities:
- Delete images that aren’t needed anymore
- Do a live migration to another disk
If you have spare disks, which you should, you can do a live migration of a VM. You can also delete images that are not in use.
Reference
https://forum.proxmox.com/threads/vm-io-error-yellow-triangle.101195/