We reported two days ago that Microsoft managed to ship Windows 11 with a known issue which caused slow drive write speeds, despite beta users complaining about it several months ago.
The issue was recently brought to light again when Reddit user PleasedPen25317 ran a series of CrystalDiskMark benchmarks of the Samsung 980 Pro SSD and showed a massive reduction in random write speeds for any partition with Windows 11 installed.
Windows 10 vs Windows 11
It now appears Microsoft has acknowledged the issue and is working on a fix.
In a support document for Optional Update KB5007262 Microsoft writes:
Addresses an issue that affects the performance of all disks (NVMe, SSD, hardisk) on Windows 11 by performing unnecessary actions each time a write operation occurs. This issue occurs only when the NTFS USN journal is enabled. Note, the USN journal is always enabled on the C: disk.
Given that the problem affects all drive, not just super-fast NVMe SSDs, the issue must have been more widespread than previously expected.
If you believe you are affected, you can try out the fix by installing KB5007262. Read more about it here.