[SOLVED] Backup to FreeNAS NFS, VM freeze

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SergejA

Active Member
Mar 8, 2018
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Hello.
I installed 3 nodes Proxmox 5.0 cluster.
2 nodes host all needed VMs and 3rd has only one VM with FreeNAS for backups.
FreeNAS has NFS share.
FreeNAS has 10GB RAM, 16GB RAIDZ2
Nodes connected via 1Gb lan.

When I start backup to NFS share, periodicaly I see read/write speed around 0-10MB/s.
2018-03-08_12-49-58 (2).png

2018-03-07_08-48-32.png

At this moment VM, which I backup, freezes. top shows iowait ~ 25
And I see messages like that:
2018-03-08_12-49-01.png


But if I perform backup to local storage, all goes OK, no freezes and speed lags.

2018-03-08_13-14-40 (2).png

Please, help me, what I have to check?
 
This sounds like a problem I had too with vzdump backup -> https://forum.proxmox.com/threads/ha-manager-vms-going-in-error-state.40766/

massive NFS writes (that's not only related to vzdump) tend to fill up all buffers and make machines unresponsible for some seconds. We observe such a behavior also with ubuntu desktops writing large (multi GByte files) to NFS Storages.

I would suggest setting bwlimit inside /etc/vzdump.conf, that helped with my problem. I had even hosts fenced by HW Watchdog during backup

maybe it is better to limit backup bandwith anyway to keep I/O stress down to keep VM's in responsive state. Backup is a good thing of course, but I think it can run in background with lower speed as long as the backups are consistent through snapshotting,
 
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