Kirk Miller

So, it has come to this...

Disable SMB 2 on Windows

Problem

Files placed on a network share may take up to 30 minutes to be visible to other users or applications that rely on network shares such as Patterson Eaglesoft or Carestream SoftDent may lock up or suffer from poor performance when sharing between Windows Vista/7/2008/2008 R2.

Cause

My personal opinion is that the Microsoft SMB v2.0 stack is broken. When everything works as it should you can achieve double (if not more) the transfer speed of the SMB v1 Windows Server 2003/XP/and below counterparts. The main cause of this issue is how opportunistic locking is handled between the two different versions of SMB. It is a bummer to have to revert back to an older, slower protocol but sometimes it is a necessity.

Solution

First you will want to disable SMB2 on all clients and servers on the lanmanworkstation side.

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sc config lanmanworkstation depend= browser/mrxsmb10/nsi
sc config mrxsmb20 start= disabled

If, in the future, you would like to re-enable it the command below will do so.

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sc config lanmanworkstation depend= bowser/mrxsmb10/mrxsmb20/nsi
sc config mrxsmb20 start= auto

Next you will need to modify the registry on the server to disable SMB2 on the lanmanserver side. I have provided a .reg file below that outlines what needs to be done.

smb2off.reg
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Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\LanmanServer\Parameters]
"Smb2"=dword:00000000

If you would like to turn SMB2 back on use the following registry entry.

smb2on.reg
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Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\LanmanServer\Parameters]
"Smb2"=dword:00000001

Lastly you will want to reboot every system that you have made changes to.

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