I'm building a series of virtual failover clusters, 2 for SQL, and 1 for BizTalk. Being that it is a Proof of concept virtual setup with no real expectations around high availability, is it possible to use the same quorum drive between clusters?
It's unlikely that you'd be able to re-use the Quorum disk for more than one cluster since each cluster will be trying to put its files in the same place.
The Quorum drive doesn't need to be terribly large (at least 512MB according to this)
Since it's just proof of concept, do they need to be separate clusters? You can have more than one SQL instance in a single cluster and I would imagine that you could have BizTalk in there too. That way they could share the same Quorum.