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Help to limit the policy of HYPERV

Created: 29 Jan 2013 • Updated: 04 Apr 2013 | 1 comment
This issue has been solved. See solution.


i'dont find a way to limit the number of backup simultany with a policy of hyperV who use a hyperV cluster and some VM associate.

The problems is the backup start in launch all the snapshot on all the clients and i need to limit the number of VM at 5 per HyperV node.

I already use the limit streaming on the node hyperV (client propriety but it's not OK).

Do you have another help for me ?


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RLeon's picture

You can try using the "Limit jobs per policy" option in the policy's attribute tab to control the number of streams coming out simultaneously from Hyper-V to the media server. However, this does not help much to limit the number of VMs being snapshotted at the same time, especially if all your .vhd (virtual hard disks) are located on the same volume.

This is because, by design, when snapshots of the VMs are created for NetBackup to backup from, VSS is used on the Hyper-V hosts. And VSS is volume based, not per-VM or per-file based.

Even if you are only trying to backup one VM, the entire volume where the VM's .vhd files are located will still be snapshotted as a whole, this effectively means that all other VM's residing in the same volume will also be snapshotted (from the storage's perspective.)

The above applies regardless of whether you are running a standalone Hyper-V host, a Hyper-V cluster with multiple Hyper-V hosts, or if you are using CSV.
The bottom line is that in Hyper-V backups, NetBackup uses VSS snapshots on the Hyper-V host, and VSS snapshots are volume based, so all VMs inside the same volume would effectively be snapshotted together.

Unless all your VMs are scattered in many different volumes, the "Limit jobs per policy" option would only help with the simultaneous data transfers. Same applies if you use the Storage Unit's "Maximum concurrent jobs" or the "Maximum jobs per client" settings. You cannot restrict a snapshot to only affect a single VM.

The following excellent article explains this for Hyper-V backups in Backup Exec, but everything it says also applies to NetBackup: