Microsoft admits it tested SQL Server as store for Exchange 2010

Microsoft Corp acknowledged that it had “absolutely” considered replacing the maligned storage engine in its Exchange e-mail server software with its SQL Server database.

But “after much debate,” the company decided to stick with the existing Extensible Storage Engine (ESE) in Exchange and issued a promise of a significant ESE performance boost in Exchange 2010, the next version of the software, Microsoft said in a blog post.

“Yes! Some very smart engineers did amazing work and we had mailboxes up and running using SQL Server,” wrote Microsoft. “It was ultimately determined that the best way to ensure we could drive compelling innovation into Exchange for 2010 and beyond was to remain committed to ESE.”

Microsoft said it has been considering swapping out ESE, better known as Jet, on and off for at least seven years.

Jet is often blamed by users critical of Exchange's scalability or performance. It has historically forced e-mail administrators to restrict user in-box sizes or engage in complicated archiving schemes.

The rise of cloud-based e-mail services that offer unlimited in-box sizes at low cost and with minimal management requirements, such as Google Inc.'s Gmail, has put pressure on market-leading Exchange to address its technical shortcomings.

At its TechEd conference this spring, Microsoft said that using an upgraded Jet database, Exchange 2010 will be able to read and write e-mails to disk 70% faster than Exchange 2007. It will also be able to store five times as many items per folder than Exchange 2007 and handle 10 times more active connections.

Some analysts are still predicting that Microsoft will switch to SQL Server in a future Exchange version, perhaps in the subsequent version slated to ship in 2013. Microsoft said that it's keeping its options open beyond Exchange 2010 and that the company is only committed “to stay on ESE at this time.”