I had the same problem when booting vm's in ovirt 4.4.0 .
The legacy bios could not detect the disk to boot up and yes as suspected was a storage
problem with gluster.
After upgrade to ovirt 4.4.1 and run again "Optimize for virt store " i dont
see this boot problem anymore, but maybe is something else ? dont know exactly what was
fixed
Thanks,
Emy