Aligning Disk Partitions by Using Diskpar.exe


Topic Last Modified: 2007-02-14

Be careful when you use diskpar.exe because it formats your disk partitions. Back up the data that you want to keep.

Microsoft Windows 2000 Server has an internal structure known as the master boot record (MBR) that limits the maximum number of hidden sectors to 63. This characteristic of the MBR causes the default starting sector for disks that report more than 63 sectors per track to be the 64th sector. Therefore, when programs transfer data to or from disks that have more than 63 sectors per track, misalignment can occur at the track level, with allocations starting at a sector other than the starting sector. This misalignment can defeat system optimizations of I/O operations that are designed to avoid crossing track boundaries.

Diskpar.exe is a command-line tool from the Windows 2000 Server Resource Kit that can explicitly set the starting offset in the MBR. By doing this, the track is aligned with the physical disk partition, which results in an improvement in disk performance. Exchange writes four kilobytes to the database and up to 32 kilobytes for the streaming data. Therefore, make sure that you set the starting offset to be a multiple of four kilobytes.