SN850 worse performance on Windows 11

I have clean-installed Windows 11 on WD Black SN850. The random write rates are much worse than in Windows 10, especially 4K Q32T16 test in Crystaldiskmark (2600MB/s in Win10, and 800-900MB/s in Win11) even with Defender and Virtualization Security turned off. If I return to Win10 everything’s normal.

I am having the same issue. When I upgraded from 10 to 11 my 4k went up to the 4000+ but after reinstalling 11 fresh (reset) I’m down to 800-900 like you.
Installing latest chipset drivers didn’t help.
Did you figure this out?

Nope, tried many things but in the end I’ve downgraded to 10. 11 is barely usable anyway, for many different reasons.

I don’t see how is 11 barely usable. For is working great except for that. But turns out I reinstalled 10 clean and I still got the same bad 4k performance… No idea what so I just moved back to 11 and will forget about it
AMD driver issues are getting on my nerves

I’d you are testing crystal mark, make sure you have settings to nvme. That was all my issue. Back to 4000+ pts in rnd4k read

That’s not it, I have these settings always.

It seems this is indeed a Windows 11-related problem that affects write speeds also of other SSD vendors. See for instance:

Then your system is messed up. Mine is working perfectly again and on Windows 11.
Real world performance backs up also my benchmark results

Have you tried to update the SSD with the latest drivers that adapted Windows 11? Or the firmware?

If the manufacturer does not release any of the new drivers then you might report this back to Microsoft Windows Insider Team via Feedback Hub. Maybe more people will report the problems and get MS to come up with a fix.