This actually happened last week, but I’ve been remiss in getting it posted (sorry, Missy!) Missy recently completed two Exchange 2007 whitepapers, both centered around the CCR story.
The first one, High Availability Choices for Exchange Server 2007: Continuous Cluster Replication or Single Copy Clustering, provides a thorough overview of the questions and issues to be considered by companies who are looking for Exchange 2007 availability:
- Large mailbox support. In my experience, this is a major driver for Exchange 2007 migrations and for looking at CCR. Exchange 2007’s I/O performance increases have shifted the balance for the Exchange store being always I/O bound to now sometimes being capacity bound, depending on the configuration, and providing that capacity can be extremely expensive in SCC configurations (that typically rely on SANs). CCR offers some other benefits that Missy outlines.
- Points of failure. With SCC, you still only have a single copy of the data – making that data (and that SAN frame) a SPOF. There are mitigation steps you can take, but those are all expensive. When it comes to losing your Exchange databases, storage issues are the #1 cause.
- Database replication. Missy takes a good look at what replication means, how it affects your environment, and why CCR offers a best-of-breed solution for Exchange database replication. She also tackles the religious issue of why SAN-based availability solutions aren’t necessarily the best solution – and why people need to re-examine the question of whether Exchange-based availability features are the right way to go.
- RTO and RPO. These scary TLAs are popping up all over the place lately, but you really need to understand them in order to have a good handle on what your organization’s exact needs are – and which solution is going to be the best fit for you.
- Hardware and storage considerations. Years of cluster-based availability solutions have given many Exchange administrators and consultants a blind spot when it comes to how Exchange should be provisioned and designed. These solutions have limited some of the flexibility that you may need to consider in the current economic environment.
- Cost. Talk about money and you always get people’s attention. Missy details several areas of hidden cost in Exchange availability and shows how CCR helps address many of these issues.
- Management. It’s not enough to design and deploy your highly available Exchange solution – if you don’t manage and monitor it, and have good operational policies and procedures, your investment will be wasted. Missy talks about several realms of management.
I really recommend this paper for anyone who is interested in Exchange availability. It’s a cogent walkthrough of the major discussion points centering around the availability debate.
Missy’s second paper, Continuous Cluster Replication and Direct Attached Storage: High Availability without Breaking the Bank, directly addresses one of the key assumptions underneath CCR – that DAS can be a sufficient solution. Years of Exchange experience have slowly moved organizations away from DAS to SAN, especially when high availability is a requirement – and many people now write off DAS solutions out of habit, without realizing that Exchange 2007 has in fact enabled a major switch in the art of Exchange storage design.
In order to address this topic, Missy takes a great look at the history of Exchange storage and the technological factors that led to the initial storage design decisions and the slow move to SAN solutions. These legacy decisions continue to box today’s Exchange organizations into a corner with unfortunate consequences – unless something breaks demand for SAN storage.
Missy then moves into how Exchange 2007 and CCR make it possible to use DAS, outlining the multiple benefits of doing so (not just cost – but there’s a good discussion of the money factor, too).
Both papers are outstanding; I highly recommend them.