There isn't a new Install Guide yet as far as I know. The version 2.3 one is current for topology requirements. Changes and some XSan 3 specific stuff is found here under Other Services.
We are planning to build a 10.8/Xsan 3 based system from scratch.
I'd call Small Tree and see what they think you need based on your budget and requirements, especially if you don't already have a bunch of FC hardware purchased.
In previous versions, the suggestion has been to dedicate an entire controller to the Metadata Volume and maybe a Render drive, is that still the suggestion?
The topology is all the same. Two dedicated MDC servers recommended, at least one required, the metadata drives should be mirrored, and everything is fibre channel. Also recommended is independent ethernet for metadata, separate from the ethernet network for internet/file sharing.
basic Xsan 2.3 install guide seems to indicate that you can use three drives from one of the Controllers that will be used for the Data Volume, for your Metadata Volume (so one controller could be used to control both your Metadata Volume and part of your Data Volume, is that correct?)
I don't know what you mean by using an MDC drive for data. XSan is a SAN, it uses fibre channel LUNs only for data.
Have they removed the requirement to dedicate an entire Controller to the Metadata Volume?
Should I just assume that the original suggestions for overall design, should hold true for Version 3,
what is the best approach to keeping all the machines timed correctly, if that can't be connected to a Network Time Server?
Server has a network time server. Set that up and point all computers to sync to it. As long as all computers are synced, it doesn't really matter if the time is correct so long as it's the same on all computers.