Sizing Exchange for Very Large Implementation

With 30.000 active users and 250.000 you already have quite a large exchange organisation, i assume your address books alone already produce quite some noticable traffic ;)

Well to come to the point - i find it quite "brave" to spread these among just 4 servers, but hey after all it is not numbers where i would say "impossible", but having growth in mind it would be the more economic solution if you at least gave a thought about having more servers.

So for your current setup you would "just" need 8 servers. And when i say server i dont mean 1U pizza box style servers, i mean real monsters. For your Exchange 2003 i would have NOT recommended it, but with Windows 2008 and Exchange 2007 you would benefit from more processors. In 2003 you would have had not much fun with having too many cores, but now here's your chance. Even 32 core systems are no problem for exchange 2007, so finally a fun machine to administrate. How many cores you really need depends on your average load, your current system should give you an impression about what you should calculate with.

If you are really having a 4/4 cluster is a question better not to discuss - one could write books about it and not have said everything. I would say the more economic solution would be to double the number of virtual exchange servers, with this you could use smaller scale single servers. At first glance this does not sound like a win, but in the long run 2 affordable midrange servers are way cheaper than the 4U monster model. This depends a bit on your supplier, but we have Fujitsu and they tend to be a pharmacy when its about "the big ones". We have one of these beasts where a single replacement backplane costs more than a small server.

However, this is much of a strategic/economic solution, after all you also double administrative overhead - on the other side if you expect growth it is much easier to avoid bottlenecks with more servers. You can also double virtual servers but not double physical servers ofr the cost of failover safety, but in your scale it is unlikely its a company that loves to save on safety. I assume you have a "Two server locations" concept, so that will most probably not be an option anyways.

I am too conservative for a virtual setup here. Yes virtual servers will give you more flexibility, but in a dedicated environment i think with good planning virtual servers would do more harm than benefit as you need to have aditional administrators or skill, have an additional "point of failure" and additional licensing cost and planning overhead. But as before - this is heavily dependant on the company strategy. My personal oppinion is that well planned dedicated systems are not a typical candidate for virtualisation.

Memory: Well with Windows 2008, 64 Bit and loads of Gigabytes of memory life can be so much more fun. Goodbye /3GB switch. Generally the more the better. For your "4 virtual servers" i would recommend at least 32 GB per machine to have fun with these. Unlike several years ago memory became so cheap it is no longer a strategic value, Good rule: If unsure just double it, unlike old 32 bit versions with the /3GB switch windows and exchange can finally handle memory in a way it should always have been.



In the end this is all my oppinion. In the end there are many possible solutions and if well planned they all lead to a happy end ;)

I will be only allocating 1 or 2 cpu's per virtual Machine, so the numbers of CPUs in the Physical machine won't be that important when considering what kind of 2k8 license to buy.