Check SSD alignment in Windows

Last Updated on August 17, 2018 by Dave Farquhar

It’s important to check SSD alignment in Windows. If your SSD isn’t aligned, you reduce its performance and its life expectancy. Fortunately in many cases, your SSD will be properly aligned, but it only takes a minute to check.

What is a 3D SSD? You can't tell by looking.
Aligning your SSD increases its life expectancy and performance. You can check SSD aligntment from Windows with one command.

If you created the partition with Vista or any newer version of Windows, 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.

To check your alignment in Vista, Windows 7, Windows 8, Windows 8.1, or Windows 10, open a command prompt and type the following command:

wmic partition get BlockSize, StartingOffset, Name, Index

Now it’s time for some math. Take the number at the end of each item. Divide it by 32768. If the result is a whole number, your partition is aligned. If it’s not a whole number, 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 2-5.

Here’s why. 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. So your drive works twice as hard. And since the drive has a limited number of write-erase cycles, its life expectancy drops. Furthermore, since writes tend to be slower than reads, you’re more likely to notice the difference. Random writes are what all drives are worst at; there’s no reason to make them twice as bad as they would otherwise be.

Are you sold on alignment? Good. If your SSD isn’t aligned, there’s a way to correct this problem and align it for free, relatively easily.

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