How to check SSD alignment

If you didn’t align your partitions when you upgraded to an SSD, there’s a pretty good chance you’re giving up performance and life expectancy. Here’s how to check SSD alignment.

But first, a bit of good news. If you created the partition with Vista or Windows 7, your partitions should be aligned. If you upgraded from XP and didn’t re-partition the drive in the process, then it probably isn’t.

Get ready for some command-line jockeying and some math.In XP:

select disk 0
list partition

Substitute the disk number in line 2 if it’s not 0. If you don’t know the disk disk drive number, you can  find out with a little mousing around. From the Start menu, click Control Panel, click Administrative Tools, click Computer Management, and then click Disk Management.

In Vista/7:

wmic partition get BlockSize, StartingOffset, Name, Index

If the starting offset is evenly divisible by 32768, your partition is aligned. If not, you’re hurting your SSD’s performance and life expectancy. How much depends on your drive and your usage, but you can reasonably expect your life expectancy to drop from 5-10 years to 2-3. If a partition is misaligned, writing one cluster to the filesystem results in writing to two blocks on the SSD, causing two erase-write cycles rather than just one.

The conventional solution (there’s a better solution at the end) is to back up the drive, boot with a Windows 2003SP1 or later installation CD or Linux live CD, then do the following (assuming you’re using some kind of Windows  CD):


select disk 0 with 0 being the number given for your ssd

clean this destroys all partition/volume data on the disk

create partition primary align=1024


format fs=ntfs quick


Sounds like work, doesn’t it?

Paragon Software also has a $30 tool for aligning partitions in place, without the need for the backup-repartition-format-restore cycle. They don’t exactly go out of their way to market it, but you can find it at

Depending on the value you place on your time, at $30, many people will find it worth the money.
Update, 28 Dec 2010: And there’s a way to do it for free, relatively easily. See How to Align your SSD or RAID array for Free.

2 thoughts on “How to check SSD alignment”

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