[Users] When does oVirt auto-migrate, and what does HA do?

[Rob Zwissler]

In what scenarios does oVirt auto-migrate VMs?  I'm aware that it
currently migates VMs when putting a host into maintenance, or when
manually selecting migration via the web interface, but when else will
hosts be migrated?  Is there any automatic compensation for resource
imbalances between hosts?  I could find no documentation on this
subject, if I missed it I apologize!

In a related question, exactly what does enabling HA (Highly
Available) mode do?  The only documentation I could find on this is at
http://www.ovirt.org/OVirt_3.0_Feature_Guide#High_availability but it
is a bit vague, and being from 3.0, possibly out of date.  Can someone
briefly describe the HA migration algorithm?

Thanks,

Rob