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Get In a Line

By Steve Jones,

http://i.msdn.microsoft.com/dd758814.image004(en-us).jpgRecently I was re-reading the disk partition alignment white paper to check something that I'd seen posted on the Internet. If you haven't read this whitepaper, I'd highly recommend it to all DBAs, especially if you run systems that have performance issues and have an OS prior to Windows 2003. Or even if they were upgraded from an older OS. It's a little tough to get through in places, but it's a concept worth understanding.

The data from this whitepaper has been around for quite a few months, but as I talk with people and mention it at times, I often see surprised looks. It seems that there are many DBAs that don't understand it, or don't think it might apply to them.

I think a 30-40% performance improvement means it's worth examining on your systems.

The technical details are a little hard to understand, but there are some fairly easy checks that can help you determine if it is an issue, and then you can decide if it's worth the undertaking to rebuild your partitions for busy systems. Considering the fact that many people still run SQL ServerĀ  instances on RAID 5 partitions, andĀ  mis-aligned partitions could create a pretty high performance penalty (up to 90% has been observed), wouldn't you want to take a few minutes and check the partitions on your busy servers?

Doing something about misalignment is a little harder. You have to rebuild partitions, which means downtime and moving lots of data around. However that could be a fairly cheap way to improve performance, especially when buying a larger server or new SAN can get very expensive.

Steve Jones

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