Advantages and disadvantages of using VDMs on VNX

You'll probably get a number of responses, but here is my opinion.  Based on nothing other than, well, my observations.

Advantages

• Dramatically enhances disaster recovery via VDM + FS replication
• Allow greater isolation of resources (CIFS servers on VDM_A are fully isolated from CIFS servers on VDM_B, from a management and filesystem perspective)

Disadvantages

• Requires foresight and planning into division of resources between VDMs (which CIFS servers to put on which VDM, etc)
• Global CIFS servers are still constrained to one VDM; no way to create a Global CIFS server across all VDMs and physical DMs

Better than a physical DM?  Yes!  From my perspective, there's no reason not to create a VDM and put your CIFS servers on it.  It simply makes replication much easier to provide failover to a DR VNX.  Even if you're not ever planning to do DR replication, simply having your CIFS servers on VDMs make it much easier to do hardware refreshes or major upgrades (e.g., moving VDMs between disk pools).