Sunday, May 4, 2008

Diskpart and Windows 2008

Microsoft claimes that there is no need to use diskpart on a Windows 2008 server with Exchange 2007 SP1. If you have build some larger servers with Exchange in the past this sounds wonderful to skip the diskpart stuff, but if you think about it for a while what exactly has Exchange to do with storage track boundaries. Exchange doesn’t know about this, it simply uses the partition presented by the OS. In my opinion this is simply a Windows 2008 server thing.

Why is Windows 2008 better than previous version of Windows?
When creating partitions with the built in Disk Management tool it created a partition that isn’t always aligned with the underlying disk layout , so sometimes when writing or reading from disk windows was forced to do two read or writes instead of one and that is of course bad for performance.
What Windows 2008 does when creating a partition is to move the starting point forward in the same way you manually did when using diskpart.exe so there should be no misalignment between the physical storage system and the logical partition layout. The storage layout has changed during the years from 32KB chunks to 64 and sometimes 256KB, Windows 2008 set the offset to 1MB to be safe in the future. Do anybody remember ‘no one should ever need more than 640KB memory’.

And yes, every application running on Windows 2008 will benefit from this, not only Exchange.

In case you’re interested in how to how to Align Exchange I/O with Storage Track Boundaries with diskpart.exe, here it is http://technet.microsoft.com/en-us/library/aa998219(EXCHG.80).aspx.
This is a must read if you don’t use Windows 2008