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Is clustering a good idea?

Expert Peter terSteeg explains why clustering isn't always necessarily the best approach to high availability.

I am working with a client migrating from eight Exchange 5.5 servers with 3,000 users to Exchange 2003. The plan was to consolidate into two active/passive clusters, splitting users into multiple storage groups on each cluster. However, I am getting some nay saying from a high-end Exchange consultant who tells me I am getting myself into more trouble than it's worth. He recommends I don't cluster, but instead put in three servers and not cluster them. I called Microsoft and they said the clustering works great -- but that is like asking Ford if the Mustang is a good car. Do you have any insight on this?
I hope I wasn't the high-end Exchange consultant who told you to avoid clustering. All kidding aside, I think clustering does work. But, I would ask yourself if you are prepared for the additional complexities that it can bring into the picture.

Running a cluster for high availability can be worthwhile if near-zero downtime is the practical goal. I think outside of a motherboard failure, you could also run independent systems and probably achieve reasonable uptime without clustering. Yes, you will need to apply and reboot machines for service packs -- without clusters. But, I would say that most companies that I've visited are not particularly ready for clustering -- nor are they extremely prepared for the complexities that the additional uptime requires.


I have run Exchange 2000 and now Exchange 2003 in a clustered environment exclusively. I didn't feel it was any more complex than setting up multiple servers and routing groups. For maximum uptime, I think clustering is the way to go.
—Justin C.


We are actually in a similar scenario, migrating from Exchange 5.5 to Exchange 2003. We want to provide high availability via clustering, and shared storage goes hand-in-hand with this. After some searching, we've found several block-based shared storage solutions we could leverage, namely NetAPP's AS250 (iSCSI SAN) and EMC CX300 FC SAN.

However, after assessing the different "failure" scenarios, we've found that, although we gain redundancy and availability via the active-passive cluster nodes, we've put all of our "storage eggs" in one basket! With proper server room considerations, the risks can be minimized or even eliminated. However, our organization does not have that "hardened basket" to shield these "storage eggs."
—William W.

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Related information from SearchExchange.com:

  • Learning Center: Exchange clustering 101 and 102
  • Reference Center: Clustering tips and resources

  • Dig Deeper on Exchange Server setup and troubleshooting

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