Windows Server 2012 slow network/SMB/CIFS problem

Add me to the list of people who had GLACIALLY slow SMB/CIFS/network file transfer performance between Server 2012 and XP or 7 clients – no idea if it would be any better with a Windows 8 client, but it was TERRIBLE (read: less than 500 KB/sec on gigabit network with solid state storage) file server performance and XP clients.

Also add me to the list of people for whom disabling mandatory SMB signing did the trick to cure the problem.


Open up Group Policy Editor, and right-click-and-edit Default Domain Controller Policy.  Go to Computer Configuration/Policies/Windows Settings/Security Settings/Local Policies/Security Options, and set Domain member: Digitally encrypt or sign secure channel data (always) and Microsoft network server: Digitally sign communications (always) to Disabled.

In theory, gpupdate /force should get the job done, but in practice I had to reboot my Server 2012 instance to make it take effect.  Once I’d done so, the difference in speed was extremely obvious – even folder listings were visibly faster, and copying a 9MB file from a share to a client desktop went from taking 20+ seconds to being instantaneous, as it bloody well should be.

Worth noting: this shouldn’t be a problem on a non-domain-controller 2012 server, as you can see from the location of the GPs I had to edit.  Also worth noting: these settings aren’t set correctly on Windows Server Essentials 2012 either, despite the fact that WSE is always both a domain controller and a fileserver.  Way to QA your products, MS… sigh.

Published by

Jim Salter

Mercenary sysadmin, open source advocate, and frotzer of the jim-jam.

13 thoughts on “Windows Server 2012 slow network/SMB/CIFS problem”

  1. Mate, you saved my life. My new backup server worked like charm (wire-speed) when copying files over network manually (105 MB/s), but shared 7mbps for SQL Server share backup, Windows Server Backup, VM import/export and so on… 2 days of internet digging and found!

  2. I have absolutely horrible transfer speed on a new gigabit switch with server 2012 R2 running Essentials. I made the change and rebooted after even forcing a GP update. The server has two GB Nics in bridge mode in the switch, and the lan speeds are horrible: a 95 MB folder is transferring at less than 89 KB. This is ridiculous: I have a new server, new switch, and the worse speed I have ever seen.

    Any other ideas than just this change? Maybe a difference with Server 2012 R2?

  3. Your description – dial-up-modem speeds over a gigabit network – sure as hell sounds like SMB signing.

    My major suggestion here is probably just not to use Server Essentials 2012. =\ The pricing makes Windows SBS, and now Windows SE, look enticing at first glance… but man, oh man, do you ever pay back HARD in the long run for those few hundred bucks you save up front. The upgrade path is a nightmare, you’re stuck with garbage like this that MS neither planned for nor cares about (because their own documentation says, basically, “you shouldn’t ever do anything with a DC other than it be, well, a DC”… and then they sell you a product that’s “hey, I’m a DC and everything else you ever need!”), etc.

    You might also be able to at least semi-confirm your issue by installing an FTP server – like Mozilla’s FileZilla, for a free example – and testing access to the same files to confirm for an absolute fact that the issue is SMB/CIFS related rather than anything-else-at-all related.

  4. Dude, you’re a legend! I have a measly little HP N40L MIicroserver running Server 2008 R2. I was getting only 3MB/s over a wired connection to the desktop that was 1 meter away, even after upgrading to a Gigabit switch. Now I’m getting a solid 75-80MB/s.

    I should add that it’s not a DC, just a simple file/media/download server (with a Linux VM running on Hyper-V) sitting on my local home network. This change still made a difference though, which is a pleasant surprise. I didn’t think making changes in the Group Policy editor would’ve affected it – but I’m not complaining! Thanks for the post!

  5. I encountered the same problem. I tried this and it seems to have partially fixed the problem. Now copying files to a network drive is very fast, but copying from the same network drive (on Win 2003) is still slow.

  6. If anybody else (including me) is still having problems with this after disabling SMB signing – I got a pingback from an Italian guy who got some benefit from this fix, and then another big bump from disabling Receive Side Scaling.

    Device Manager ==> [Network Card] ==> Advanced properties of the physical network adapter (or virtual network adapter that manages the ” Team “of the physical NICs) ==> select RSS (Receive Side Scaling) and then set it to DISABLED.

  7. Windows Server 2012R2 gives really terrible network speed.

    I manage 11 websites and use Windows.

    Before Windows 2008R2, there’s no problem. Only 2012/2012R2 has network issue.

    SQL transfer speed(from master > clients) is also.

    I gave up the 2012R2 and rolled back to 2008R2.

    I tested many Intel lan cards from Pro1000et….. but results were same. Even iSCSI protocol.
    And I detached the L4 router and only connect via L2s(Cisco/NetGear) and same result.

  8. I just went through this yesterday, and I’m happy to throw another “gotcha” in the mix….Especially since this was the top search result when I queried “slow copy server 2012”.


    Dell R720 running Server 2012 Standard R2 and Hyper V
    Virtual Server running Windows Server 2012 Standard R2
    All switches are gigabit, ~25 node network.

    Users reported slow performance with pretty much any operations with server files and folders. The example shown to me was a folder with some subfolders and files, all totalling a whopping 1.4mb. Copying this file to another location on the server was taking ~5 minutes. Deleting the same folder took about as long. Data transfer rate rarely went above 100kb/s.

    Tried all the steps above (thanks), but what it ended up being was the simple fact that the V-Host machine was running a Broadcom NIC, and it doesn’t play well with a feature (new to Server 2012) on the virtual server’s NIC called “Virtual Machine Queues” (VMQ). In our case, the feature had to be disabled on both the virtual NIC of the virtual server and also the physical nic (the Broadcom) on the V-Host.

    The issue is described at:

  9. I had tried changing group policy as well but did not work. What worked for me was Jim Salter suggestion to disable Receive Side Scaling. Network speed is now blazing :). I have not reversed the settings done on Group Policy, which I will try once some application work is done to ascertain of disabling is enough or it’s a combination effect of group policy change and RSS disabling.

    Thank you,


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