Where Should my CAS servers go?

Today’s Question | I have four Dell servers. We are installing Exchange Server 2007. We are going to implement CCR. What should we do with the other two servers?

Answering this Question proved to be harder then you might think. Harder, due to all of the server implementation options available with Windows Server 2008 and Exchange Server 2007. In thinking about this question, a number of thoughts ran around in my head before I landed on a good answer. Once I thought that I had a good answer I consulted a group of fellow Exchange geeks who provided me with more ideas and things to think about. After wading through their ideas and my own, I finally come up with two answers that I stand behind

Answer One – Hyper-V

It is my personal feeling that all servers should be built as virtual servers. My main reasoning behind this thought is that this makes your server installs hardware agnostic, and whole server backups are simpler. With hyper-v if you want to add more hardware to a server you don’t have to build a new one and migrate to it anymore. With virtual servers If you need more power you reallocate resources to the virtual or you move the virtual to a new server; no more build new server and migrate. I like to kick this up another notch and implement my virtual server host servers as clusters; that’s a story for a different post.

I would build this four server deployment as a four node clustered Hyper-V server. I would install the two CCR nodes on node 01 and node 02 of the cluster.  I would install a CAS and Hub Transport server on node 03 of the cluster, and Node 04 of the cluster would be the passive node. This implementation would look this:

VM Cluster

This is the more redundant and expandable configuration of the two options, but is also the most complicated. That extra complication can lead to less downtime if you are not prepared for a cluster. I do not recommend this implementation unless you are very comfortable with Microsoft Clustering services. That being said, I have built this setup before and I have always been very happy with the functionality.

Answer Two – CCR + NLB

Solution two offers a less expensive high redundancy solution. I offer this as option two because I like the hyper-v option better for it being hardware agnostic. On a big cost savings note. this solution does not require shared storage for the Hyper-V MSCS cluster; this could be a big deciding factor for some ( 2-100k+ in cost for the NAS depending). In this option I would install CCR on server1 and server2. I would install the CAS and Hub Transport server roles on server3 and server4 and implement Windows Network Load Balancing (NLB) on both serves. NLB  is supported on both roles post SP1, prior to that it was only supported on the CAS server role. This implementation would look this:


Either of these solutions would be a great way to setup Exchange Server 2007 with four servers. Which one you choose depends on your personal preferences and comfort level with the technologies— happy installing.

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