segmentation of VM

You've kind of lost me there, what do you mean by segregating across hosts?

So, are you wanting to have a number of VM's go to one domain controller and another bunch go to another or?

I mean for example if you have 2 domain controller VM's that they arent on the same host, that kind of design strategy.

Ohhh I see what you're saying now

Ok so, right click the cluster that you want to do this on, go to edit settings, then to DRS group manager. Put all your domain controllers in a single group.

Next go to Rules Add the group into the rule and then select separate virtual machines.

That will ensure they don't go on the same host :D

It's common sense, to ensure that your Domain Controllers and Exchange Servers are "spread" across different hosts in the farm.

We've discussed this before, with DRS and the use of Affinity and Anti-Affinity Groups. if you have DRS, if you do not have DRS, it makes common sense "not to have all your eggs in one basket".

If you can let us know the number of VMs that you have in your network and the role that they play; Experts (designers) will be able to provide suggestions and recommendations.

That will definitely help you avoid single points of failures, HA at its best, and other recommendations to keep your network UP most of times OR minimize downtime to max possible value :-)

I was just hoping there may be a vmware specific guide/best practice in this area..

I told you the best way to do it though, did that not work for you?

I'd prefer some formal vmware documentation to site as "best practice",you'd also only mentioned AD, I wondered what other types of system are stored on seperate hosts.

Ok thanks Alex, will split points shortly