Sunday, March 4, 2012

SyncBack hang/freeze on Windows 7 - SMB version problem

Problem: SyncBack Free is a brilliant free tool for synchronizing two folders' contents fast and accurate. I had been using a Windows XP computer with two network cards standing as a bridge between two networks to sync folders between two computers residing on each side of the bridge. Old of age the XP computer were looking forward to its retirement as a young Win7 computer were set up to take over its place. The same SyncBack running the same SyncBack profile on the Win7 computer completely hung the SyncBack process within seconds after syncing was attempted. Only a reboot would kill the process - not even Task Manager managed to take it down.

Factors in the picture:
  • The two remote computers were running Win7  and Server 2008 R2.
  • Syncing between a local folder on the Win7 computer and one of the remote computers would work. Just not syncing between the two remote computers.
  • It made no difference whether Windows Shell (on the Copy/Delete tab) was used to sync or not.
  • Copying files between the remote computers from Windows explorer works just fine.
Problem reason: The reason proved to be SMB version. WinXP uses SMB 1.0, whileas Win7 uses SMB 2.0. For some reason, SyncBack does not manage to copy files between two remote computers as long as the computer is set up to use SMB 2.0.

Solution: Disable SMB v. 2.0, forcing the Win7 computer to revert to using SMB 1.0. This excellent article on Petri explains how - or here in short: From an administrative command line window run the following commands and then reboot to activate (Observe that "bowser" is actually correctly spelled - or rather, it is spelled the way that the computer understands):
sc config lanmanworkstation depend= bowser/mrxsmb10/nsi
sc config mrxsmb20 start= disabled
If you need to revert to SMB 2.0, use the following commands:
sc config lanmanworkstation depend= bowser/mrxsmb10/mrxsmb20/nsi
sc config mrxsmb20 start= auto 
I have not put any effort into researching whether security is an issue with these settings or whether other functionality is negatively affected, for me it gave me what I needed, so I am happy.