Disk Alignment Check Utility & How to use diskpart to format your partitions with correct alignment

By tom on March 2nd, 2010

Paul Randal blogged here about how you can use diskpart and wmic to check if your partitions are correctly aligned. Calculating the offset is easy when using disks, but can be a little bit difficult if different partitions on a disk are used.

Tom Hirt of tcpdump.com wrote a great little tool which calculates the offset and displays whether or not your partitions are correctly aligned. You can download it here (registration required).

A screenshot of the tool showing Non-aligned partitions:

A screenshot of the tool showing aligned partitions:

If your partitions are not aligned, you can use diskpart to format them with correct alignment. Be careful, following steps erase the selected partition and reformat them. Make sure you have a backup of all your data before proceeding!

Open a command prompt

Type diskpart

Select the partition you want to align: select disk <DiskNumber> (you can check which disks are available by typing list disk)

Align the partition to 1024KB: create partition primary align=1024

Assign a drive letter to it: assign letter=<DriveLetter>

Now you can format your disks as usual, but with a correct offset. Please note that the procedure above only works for basic disks.

I hope this helps,

Tom