2 node cluster

Hi all,

I plan to configure a 2 node cluster based on 2 Dell servers and a MD3200 DAS (via SAS link).
I'm looking for HA, so I need a quorum disk.
The (stupid) question is: the quorum disk should be used via iSCSI from a VM running in the cluster ?
What happen if the quorum disk fail (example the VM crash) ?
What happen if I don't have a quorum disk ?

Thanks in adavance.
PieroB