Virtualising Windows Domain controllers?

[Five_Star]

What are the recommended setups when virtualising Windows Domain controllers?

In a small setup with 2x physical servers both with virtualised clients will this work?


Server 1 physical (host) DC
-- Server 2 virtual (client) DC
-- Server 3

Server 4 physical (host) DC
-- Server 5 virtual (client) DC
-- Server 6

The idea being that either of the physical machines can fail / off for maintenance and the other one can carry on validating requests. The virtual client DC machines are there purely to hold a backup of AD global catalogue.

 

[Five_Star]

I left out the fact the client already has a SAN, they are wanting to do hot failover using Hyper-V for all virtual clients.

My diagram is also not 100% there are actually 4x virtual clients per physical box

I've read about the circular dependency you can get by joining the physical machine to a virtual domain so thought it best to have a DC on both a virtual and physical machine per hardware box.

I guess my choices are really DC on each of the physical machines, with virtual machines as domain members
or
One virtual DC on each hardware stack with the physical machines left in a workgroup (they will be core installs anyway, just to host the Hyper-V role)

 

[Five_Star]

Yeah, I would say its overcomplicated, I guess they are worried about having a situation where no DC is available for client requests. Its made my head hurt reading the technet forums on all the different configurations this afternoon hence asking here for a sensible answer

Seeing as we have a SAN to play with I'll test this tomorrow morning to show them how we can simplify it.

 

[Five_Star]

Can I offer them a figure for the computing power wasted if they choose to run these unnecessary DCs? 5%, 10%, 15% overhead?

Just so I've got some plus points to use in the meeting when I suggest they are dropped as waste of hardware resources.