A. Exchange 2010 has a new I/O pattern that results in 70 percent lower I/O requirements than Exchange 2007 (and Exchange 2007 had 70 percent lower I/O requirements than Exchange 2003!). This reduced I/O pattern, thanks to optimizations that make it so writes don't come in bursts anymore, combined with advancements in SATA drives, means SATA is now a realistic storage platform for Exchange 2010. SATA was previously just for desktop systems.
In addition, with the new database availability group (DAG) for high availability of mailboxes, the new guidance from Microsoft is that if you have databases replicated on at least three servers in the DAG, you don't even need RAID on the storage anymore. Because you have backups of the data in essentially real time on the mailbox duplicates and Hub Transport dumpster, you can use just a bunch of disks (JBOD) configurations. If you don't use DAG or have only two servers replicating a database, you should still use RAID for the database. RAID was previously used for I/O purposes in addition to high availability, but because of the drop in I/O requirements, single disks are now an option. Microsoft is suggesting one disk per database/transaction log going forward, providing you have the database replicated between at least three servers.
It's still very important to perform sizing exercises to ensure that, even with the reduced I/O, pattern the disk configuration will meet requirements.
An illustration of acceptable storage solutions for Exchange from 2003 to 2010 is shown here.
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Using SATA makes it easier to allow users to have bigger mailboxes without excessive storage costs, even if you need three separate copies. Also with SATA, you can consider not performing backups anymore. Now you can high availability through multiple copies of the database, configurable lags in replay of transaction logs on certain copies (meaning we have copies of the database that look like the database some number of days ago), archiving, and the protected dumpster protection for deleted items retention. For some companies, performing a backup may no longer be required, if all the right configuration and procedures are in place.
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