Failover Clustering Quorum - Disk Witness

I have a question in regards to Windows Server 2012 R2 Failover Clustering.

Does anyone know any of any documentation or have you had personal experience with configuring a disk witness for a quorum? I’ve read in "Mastering Windows Server 2012 R2 - Sybex" that I can create a LUN to map out a drive on my shared storage and it should be 512MB. We use a 24 bay SAS as central storage for a two-node cluster and this is a possibility for clustering.

HOWEVER,

I was wondering if it is possible to use a separate server that is outside the cluster(different hardware, firmware, and drivers) as a witness for the quorum.