Thursday, June 25, 2009

Proper Disk Alignment: Windows 2003 & EMC Clariion SAN

For best performance on Microsoft Windows 2003 (SP1 or better) on an EMC Clariion SAN, make sure the disk alignment of the LUNs is correct. I found the information on the following sites, including some performance testing and some diagrams in case someone is interested. This is mostly being documented for future reference.

Performance Tests
Clariion blogs: Disk Alignment

If you have Microsoft Windows 2008, you do not need to worry about this, disk alignment is done properly by the O/S without any intervention from the user.

Once the LUNs have been presented to the host, follow these steps.
  • Open command prompt and run DISKPART
  • From DISKPART, select the LUN/Disk that you want to align with the command SELECT DISK 1. Make sure you select the correct disk. To view a list of available disks, run the command LIST DISK.
  • Once the disk has been selected, run the following command: CREATE PARTITION PRIMARY ALIGN=32. This will correctly set the alignment on your drives.
  • You can now exit the DISKPART utility and format the disk from the Disk Management interface in Windows.