RHEV 3.0: NFS ISO storage performance issues

I install my VMs via an unique (e.g one per VM) small bootable image (around 40MB).
This works without any  issues.

However, trying several at ones causes issues. 
First it causes VMs to stop responding:
VM is not responding.

Trying to mount a different ISO to a different VM when this have happend gives me this error:
Failed to change disk in . 

At this point I can't install any machines at all.

To solve this I have to:
Shutdown the VM(s) that reported "not responding".

The most annoying part is that when this have happend the affected VM(s) is really hard to stop (from RHEVM. Haven't tried to kill the proc on the RHEVH).
It's like the whole VM freezes (console doesn't work, and the machine will be in powering down state for a long time).
When the VM finally goes to "down" state everything goes back to normal, i.e I can mount ISOs again.

Anyone else who experienced anything like it?