[ovirt-users] How does ovirt handle disks across multiple iscsi LUNs

A possibly obvious question I can't find the answer to anywhere—how does ovirt allocate VM disk images when a storage domain has multiple LUNs? Are these allocated one per LUN, so if e.g. a LUN runs out of space the disks on that LUN (only) will be unable to write? Or are these distributed across LUNs, so if a LUN fails due to storage failure etc the entire storage domain can be affected? Many thanks in advance, Peter