proxmox backup (vzdump) parallelism ?

[RolandK]

is there a way to limit backup parallelism/concurrency in a cluster?

i have 5 nodes and when they all have vzdump run in parallel, our nas is heavily saturated and each of the backup "threads" is running slow

 

[dylanw]

At the moment, there isn't. However, you can configure a bandwidth limit for vzdump to reduce the load on the NFS server. See the 'bwlimit' option for vzdump [1]. There has been previous discussion regarding the topic on our bug tracker [2].

[1] https://pve.proxmox.com/pve-docs/pve-admin-guide.html#vzdump_configuration
[2] https://bugzilla.proxmox.com/show_bug.cgi?id=3086

 

[RolandK]

thanks for the pointers.

limiting bandwidth for vzdump is no option, as limiting backup bandwidth also limits VM io bandwidth, afaik.

 

[dylanw]

The bandwidth option imposes a limit on disk I/O during the backup, so it's not a general limit on VM disk IO, but it would cause additional slowdown during the backup.

 

[RolandK]

yes, and that is the culprit.

it's not such a big deal for me if backup slows down VM disk IO, but slowdown is even growing with the number of cluster nodes and there is nothing you can do against it (without slicing your backup jobs into groups).