Microsoft is currently testing a fix for Windows 10 bug that could cause the operating system to defragment solid state drives (SSDs) more often than is needed. While periodic defragging of a mechanical hard disk drive (HDD) is a good thing, doing it too often on SSDs can actually degrade their integrity and shorten their lifespan.
In simple terms, defragging is the process of relocating scattered bits of data on a drive so they sit next to each other. It has to do with how data is written on drives. Data is written in blocks on your storage drive, and the more you access files, the more scattered they can become on your hard drive or solid state drive.
This scattering can lead to reduced performance on an HDD, because it takes time to spin the platters and fetch pieces of files from very different places on the disk. Defragging organizes those blocks so that they are next to each other for faster access (HP uses the analogy (opens in new tab) of a closet full of boxes containing clothes, and is worth reading for further clarification).
SSDs behave differently—there are no moving parts or platters, and the NAND flash memory cells can only be written to so many times. Therefore frequent defragging can actually reduce the lifespan of an SSD.
As spotted by Bleeping Computer, when Microsoft rolled out the May 2020 update for Windows 10, it introduced a bug to the Optimize Drives feature causing it to incorrectly determine the last time a drive has been optimized. When you open it up, you might notice your SSD says "Needs optimization" even if the routine was recently run (Windows 10 handles this automatically).
What ends up happening is Windows 10 defrags your SSD each time your reboot your system. I was able to confirm this on my own PC, though fortunately, I hardly ever reboot. Where this is most harmful, however, is for users who turn off and turn on their PCs daily, which causes Windows 10 to defrag their SSD once a day in some instances.
According to our friends at TechRadar, Windows 10 is usually able to discern whether to defrag or run a harmless TRIM process on a drive, depending on its type. But if volume snapshots are enabled (so you can revert to a backup using System Restore), it will in fact defrag the drive even if it is an SSD.
Regardless, Microsoft has a fix in place, which has been implemented in Windows Insider program.
"Thank you for reporting that the Optimize Drives Control Panel was incorrectly showing that optimization hadn’t run on some devices. We’ve fixed it in this build," Microsoft says.
Apparently Microsoft is planning to roll out the fix to the general public with an upcoming update. At this point, it's probably best to hang tight. However, you can sidestep the issue by typing 'Defrag and Optimize Drives' in the Windows 10 search box, then highlight your SSD, click 'Change settings', and uncheck 'run on a schedule'.