Slower SMB read performance for large files in 22H2
Published Oct 03 2022 10:35 AM 19.6K Views
Microsoft

Heya folks, Ned here again. There is a performance reduction in 22H2 when copying larger files from a remote computer down to a Windows 11 computer or when copying from any Windows computer to a remote Windows 11 computer. 

 

Fix update 11/28/2022: The preview fix for this issue is now available in Windows 11 Insider Preview Build 25252. The final fix for Windows 11 22H2 production computer will come in a normal monthly Cumulative Update through Windows Update once validated in Insider builds.  

 

For the latest information about this issue, please see the known issues section of KB5017389

If you are using Microsoft 365 admin center and have Windows Release Health available there, you can view this issue in the Windows 11, version 22H2 section. The ID on Microsoft 365 is WI442499.

27 Comments

Thanks for letting me know and bringing the temporary solution. :happyface:

Regular Contributor

Hi @Ned Pyle thanks for letting us know.

 

May I share some thoughts and questions? 

 

1. Could it be the "lazy-writeback", introed and enabled by default since 1809 builds could be a cause?

 

Even when not utilizing SMB over network but usual local copy jobs e. g. from / two nvme one might notice a massive jigsaw effect when copying solid bigger files, especially with File Explorer, not so much with Robocopy as of its nature of multithreading.

Unfortunately there is no flag such as ADMX / CSP to disable lazy write-back for Explorer, to revert to the default behaviour of Windows Client and Server versions before build 1809.

The fact unbuffered IO does help, could be indicating this. 

 

2. Could you exlude the now wider default use of SMB compression, to be a potential cause for the issue? 

 

Microsoft

I can't share too many details yet, but we know exactly where it is getting slower in Kernel, nothing to do with SMB or compression. 

Established Member

I would just want to correct 40% slower statement from Ned, im seeing way over 100% difference on setups like 10gb NICs (5gb/s vs 2gb/s) difference, or on SMB multi channel setups with multiple gigabit NICs.

Microsoft

@ivicask Thanks, I'll make sure that's clear above. The variance can be quite large

Senior Member

Thanks for letting us know, @Ned Pyle!

Pedro

 

Occasional Visitor

@Ned Pyle

Can this issue cause the copied data to arrive corrupted on the destination drive?

Microsoft

Not to our knowledge. In fact, it should make corruption less likely

Occasional Visitor

Was this fixed in KB5019509?

Microsoft

@jfm666 No changes yet

Regular Visitor

Is Windows 10 22H2 equally affected or just Windows 11 22H2? What's the ETA of the fix? I am holding off upgrading Windows 11 systems to 22H2.

Microsoft

@guhoo Windows 11. I don't have an ETA from the team that owns this code, it's not my own. 

Established Member

@guhoo  Tested on Windows 10 22H2 is not affected and copies full speeds as usual. 

Regular Visitor

What is the ETA for the fix? It's been 3 weeks already and this is a very high profile bug in Windows 11 22H2.

Microsoft

@guhoo I cannot share timelines, sorry.  

Frequent Visitor

Even though I have excluded source and destination in windows security real-time protection, disabling it completely gave back most of the nic throughput.

 

Having this regression around for an entire month, is uh, disappointing...

 

 
Senior Member

I have Windows Security disabled. Transfer speeds are still cut by 50%.

Frequent Visitor

My NIC performance is reduced at least by 50%.  WiFi unaffected.  Have tested on multiple Win 11 22H2 PC's, multiple routers, multiple branded NICs - same results. 

Frequent Visitor

Correction.  WiFi performance is degraded as well.

New Contributor

slowdown SMB copy problem continues (as in not fixed), even with newly released KB5019980 update for Win11 22H2 as the problem is still noted there.

Regular Visitor

It shows a lack of concern for this flagship desktop OS.

Occasional Visitor

Dear Microsoft team when will this severe bug be fixed ? Frankly this has taken too long to fix at this point. Please update us on when we can expect the fix ? Thank You

Regular Visitor

I think it's time for Elon Musk to acquire Microsoft to light a fire under them.

Someone said once: "Feedback is a gift.". 

@Lance Longreen quality feedback vs @guhoo any helpful feedback.

Microsoft

See updated note in the blog post. The preview fix for this issue is in Windows 11 Insider Preview Build 25252

 

The permanent production fix will come in a normal monthly cumulative update after this is validated. As I've mentioned before, the fix is not in SMB, and since it's not a component I own, I don't have further details on timing. 

Regular Contributor

Good to hear. Thanks for the follow up Ned, much appreciated. 

New Contributor

thanks Ned.

 

though the fix didn't seem to make it onto the recently released 22621.1020 & 22623.1020 insider preview beta builds, just only with insider build 25252

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Last update:
‎Nov 29 2022 12:20 PM
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