A. This is a tricky one. In every Exchange 2010 document, you see direct attached storage (DAS) as the storage medium for Exchange 2010. This is for a number of reasons:

  • The I/O requirements of Exchange 2010 are 10 percent of what they were for Exchange 2003, 30 percent of what they were for Exchange 2007. This means the I/O benefits of a SAN are typically no longer required.
  • The single copy cluster model in Exchange 2007, which required the database to be on shared storage, is no longer supported in Exchange 2010. The only high availability configuration requires every node to have its own copy of the database.
  • DAS is typically much less expensive to purchase than SAN storage.

That's not to say you can't use a SAN for the storage of mailbox data. SANs still have advantages over DAS in terms of

  • Higher disk utilization (when you have dedicated storage on each box a higher percentage is left empty).
  • Central point for backup and generally faster backup/restore technologies.
  • Single point of management.

If you already have a SAN or want to consolidate storage, then you can certainly use a SAN for the storage of Exchange 2010 databases. However, the key item is to make sure you'd don't have any single point of failure. You shouldn't have each Exchange server in a Database Availability Group (DAG) storing its replica of the database on the same SAN, as this makes the SAN a single point of failure (unless you have SAN replication going on behind the scenes).

Look at the messaging for Exchange 2010. Ideally, you should use DAGs with at least three copies of every database. That is a lot more storage and a lot more mail servers, and these servers will all be running enterprise editions of Windows and Exchange, which isn't cheap. The use of DAS over SAN helps offset the cost of additional hardware and licenses.

Many organizations may use the SAN for storage of one copy of the data and then DAS or another SAN for other copies. You can mix DAS and SAN.

Long story short, SAN is supported, but you need to make sure you don't make the SAN a single point of failure. When designing your storage, consider the points of failure, backup, and I/O.

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