To improve processing capabilities, we are looking at creating multiple servers that share a a common storage. As an example we would like to have one VM server take care of moving documents and provide IIS services for external users, and the other server to provide user support but share the data the first server captures.
If you're planning to do this with Windows VMs you'll need some sort of clustered file system. I've done something similar with MelioFS from Sanbolic using the software iSCSI initiator from within the Windows VMs to access a common iSCSI target and it works well. You may also be able to use a physical RDM shared between the VMs, but I've never attempted it.