What you describe does not seem like a Proxmox specific problem to me.

You turned off the NFS server without dismounting the volumes from the nodes.
This causes IO to those NFS volumes to stall.

Proxmox does periodically check the backup directories, so there is consistent IO to them.

Since that IO cannot complete, it causes processes to hang.
I've even seen Linux not perform IO to local disks when IO to NFS is stalled for a period of time.
I am sure you can envision the horrible problems this can cause.

Using NFS soft mount might help prevent this problem but that can also cause corrupted data.

My suggestion to help avoid this is to use a vzdump hook script to mount the NFS volume only when performing a backup then dismount it at completion of backup. Better yet, setup HA NFS.




On 01/29/2014 10:33 PM, Cesar Peschiera wrote:
Serious problems with the PVE Cluster
----------------------------------------

@any developer that can help in the code:

I had problems with 2 of 5 PVE Hosts in a PVE cluster when the NFS Backup Server was shutdown manually (without that "KVM Live Backup" is running in the PVE Hosts),

The symptom was:
2 PVE Nodes were disconnected suddenly of PVE Cluster
The PVE GUI shows leds in red for the nodes without connection to PVE Cluster

To return to normal operation:
Only was necessary start the NFS Backup Server

I mean two stuff:
1- If "KVM Live Backup" is running in the PVE hosts while that NFS Backup Server is shutdown suddenly, the problem would have been more serious. 2- The PVE Cluster not must depend of NFS Backup Server to run correctly, this situation is "VERY SERIOUS"

For these reasons i think it will be necessary to correct the code of PVE Cluster

Awaiting a answer, i say see you soon

Best regards
Cesar


----- Part of Original Message ----- From: "Alexandre DERUMIER" <aderum...@odiso.com>
To: "Cesar Peschiera" <br...@click.com.py>
Cc: <pve-devel@pve.proxmox.com>
Sent: Wednesday, January 29, 2014 2:31 AM
Subject: Re: [pve-devel] KVM Live Backup performance


And the fifth question:
What will happen if this NFS Server suddenly decomposes while "KVM Live
Backup" is running?

mmm, good question....I don't known what happen when backup job is hanging because of unavailable storage...

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