Here’s an interesting thread emerging from the Windows press. A growing number of outlets are reporting that Microsoft’s own NVMe drivers run slower than their Win10 counterparts on identical (and other hardware). If Windows 11 sports slow NVMe driver, what can users do? Not much, it turns out, unless they can run a third-party driver instead (e.g. Samsung NVMe Controller). For good coverage on this topic, see Taras Buria’s recent WinAero story “Windows 11 apparently slows down NVMe SSDs.” It cites a range of interesting and informative original sources.

If Windows 11 Sports Slow NVMe Driver, Then What?

What appears to be affected is the OS boot/system drive (usually C:, where Windows itself resides). Some independent tests show that other non-OS partitions don’t suffer performance degradation. But OS partitions could suffer from reductions in random read/write speeds of 50% or worse. For grins I compared CrystalDiskMark stats from my 11th gen Lenovo X12 Hybrid Tablet running Windows 11 to my 6th gen home-brew Z170-based desktop. The former has a WD SN530 1 TB SSD, while the latter has a Samsung 950 1 TB SSD.

As you can see in the lead-in graphic, the newer Windows 11 unit is a bit slower on most readings than the older Windows 10 PC. Indeed QD32 random reads  are about 1/3 slower. That said, random writes of the same ilk go the other way (but with a less-than-7% delta). For random reads/writes with QD1, 11 edges 10 on writes by just over 9%, and vice-versa for reads by just over 15%. Kind of a wash, if you ask me.

What This Means for Upgrade Plans

MS has acknowledged that the issue is known to them and that they’re working on a fix, ETA unknown. Some reports aver that this phenomenon justifies postponing upgrades until a fix is in. My own experience with Windows 11 has been uniformly positive so far, NVMe performance observations notwithstanding. I’d recommend rethinking upgrades on PCs with heavy I/O workloads (e.g. CAD, AI, data analysis, and so forth). But for routine personal or productivity computing, it doesn’t really seem to make a noticeable difference.

I’ll be watching this issue as it unfolds. Count on me to let you know when this situation changes. Given the importance of NVMe to modern computing workloads, lots of people will no doubt follow this carefully and closely.

Note Added December 10: KB5007262 Fixes Issue, But…

KB5007262 should be installed as part of the upcoming December 14 updates for production Windows 11. It came out for Beta/Dev Channel users in November (ditto for production versions, as a Preview Update on November 23). Indeed, it seems to fix the performance issues. According to this WinAero story, the MS bugfix info for the KB5007262 announcement includes the following text:

“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.”

And indeed, on my X1 Extreme laptop (8th gen i7, Samsung OEM 512GB NVMe SSD, 32 GB RAM) speeds are where experience teaches me they should be. According to the afore-linked story, this fix applies to all versions of Windows 11 except Dev Channel. As far as I can tell, that version remains subject to the slow-down. I’m looking for some additional word from MS on this topic. Hopefully, they’ll fix it there soon, too. Stay tuned!

Back in late August, Microsoft sent an email to Windows Insiders. It indicated that the company would “soon be flighting early development builds in the Dev Channel.” That e-mail was reported by an Italian TV station, HTNovo. In fact, it’s the source for this story’s lead-in graphic. The next line in the email reads “These builds may be less stable…” With the last few (2 or 3) releases, this Dev Channel instability promise starts manifesting itself. At least, on my Lenovo ThinkPad X12 Hybrid Tablet, anyhow.

Dev Channel Instability Promise Starts Manifesting Exactly How?

Two Builds back — namely 22458, installed on 9/17 — I noticed my X12 start getting laggy and draggy. Click on a Start menu item, and there’s a noticeable pause before it opens. Double-click inside an application — Explorer, for example — and it takes one or two seconds for the drive or folder to expand and show its contents.

I’ve also noticed that the Belkin Thunderbolt dock on that PC is running at about half-speed. I’m seeing data transfers closer to 500 Mbps in Macrium Reflect, and around 70-80 MBps in Explorer for large file transfers. Wired Ethernet is topping out at under 100 Mbps on my nominal GbE Internet connection, which routinely delivers 600-800 Mbps on other wired connections. The same dock runs much faster on a Windows 10 PC, and a USB-C NVMe attached to the X12’s other USB C port directly (no intermediating dock) also runs much, much faster.

Learning What “Less Stable” Means

The weird thing is my older, less capable X380 Yoga (8th gen Intel CPU Thunderbolt 3) isn’t slowing down as much as the X12. That newer tablet includes an 11th gen Intel CPU, faster RAM, and a Thunderbolt 4 interface. My gut feeling is that the penalty must be related to newer-gen drivers and interfaces. My hope is that MS works out the kinks sooner, not later.

I installed the latest Build (22468) yesterday. It is much less laggy and draggy than the preceding 22463 and 22458 builds. But it’s still not “nearly instant.” My Beta Channel test PC (another X380 Yoga) is snappy and even a bit faster than it was when running recent Windows 10 builds.

So right now, I’m having fun. I’m observing performance, looking for potential issues and causes, and giving the new builds a good workout. I don’t mind — it’s what I signed up for when I joined the Insider Program. But it is worth noting and reporting on. I’ll keep you posted as things change and develop further. Please: stay tuned!