Hi,
Woody didn't give a step by step guide, but, assuming you know how to set up SBS 2011 and AD, probably something better, some really sound advice:
> If I had more then one physical hard disk in a system then I would not store my virtual machines on the system volume.
This is the biggest key to performance, I don't know how much peformance and reliability you need, but moving your VM(s) off of the HD which your Mac OS X uses will avoid disk contention. If you have the budget, consider SSD card(s) for better performance, perhaps even only for the Mac OS.
Your Mac Pro holds 4 drives (easily, more if you do unconventional things). Drives are cheap and if you don't have many VMs you can even run a separate VM on each drive. Of course, you can run many VMs on the same HD, and on the same HD as your Mac OS, but you can't fool mother nature and unless it's an SSD, you'll have disk contention before you peg your CPU.
If you are using spinning disks, remember that a partition is not the same thing as a disk. Running 2 VMs (or a VM and Mac OS) in 2 partitions on a single 5400 RPM disk is not going to help over running them on the same disk in one partition. Splitting them onto different disks (hopefully faster?) would help. Larger disks with less on them, at the same RPM can do well, too.
If you take care of disk contention issues, adding RAM may help. Once you are up and running can use Activity Monitor to see how much you have free and add more RAM, if needed.
> If I was replacing a physical server with a virtual server then its network would be configured as bridged and I would do then just as if it was a physical machine when it come to configuring it and allowing user access and the users wouldn't be unaware that it's virtual and hosted on a physical machine.
Yes, by all means, set this up as if each VM were a real, separate machine, test, and proceed. Virtualization should allow you to treat these issues as if you were dealing with physical hardware, down to using disks, how much RAM to give the VM, etc.
> As far as backups go I'd use no less then all industry standard methodologies from within the virtual machine as well has keeping the virtual machine backed up on a regular basis so as to have no less then two avenues of restore if/when necessary.
Absolutely! Disk mirroring not really 'back up'. What if you have a lighting strike and toast the whole machine? A flood? Theft? A write error? For some scenarios it is enough, but if you are betting your business on this, use back up, just as if you had everything running on real machines.
If you can't swing the budget, consider, at least, periodically copying all VMs (which should be encapsulating everything) a HD, removing it, and storing it in a safe location. I'm sure that would not cover many situations, and will probably raise howls of pain from IT staff on the forum, but it would be better than mirroring alone (unless is make you complacent, of course!).
It sounds like you can do it, remember to test and experiment with your setup.
So I expected what I said to not completely address your queries. 