[Users] Is it possible to limit migration speed and number of concurrent migrations?

[Dan Kenigsberg]

On Fri, Nov 29, 2013 at 11:49:05AM +0100, Ernest Beinrohr wrote:
> I want to put some of my hvs to maintenance, but that causes a
> migration storm, which causes an temporary unavailability of the hv
> and ovirt fences it, while migrations are still running.
> 
> So I have to migrate one-by-one manually and then put the hv to maintenance.
> 
> Is it possible to limit migration speed and number of concurrent migrations?

You could set max_outgoing_migrations to 1 (in each
/etc/vdsm/vdsm.conf), but even a single VM migrating may choke your
connection (depends which wins, the CPU running qemu, or your
bandwidth).

Currently, your only option is to define a migration network for your
cluster (say, over a different nic, or over a vlan), and use tools
external to ovirt to throtle the bandwidth on it (virsh net-edit
<network name> and http://libvirt.org/formatnetwork.html#elementQoS can
come up handy). ovirt-3.4 should expose the ability to set QoS limits on
migration networks.

Dan.