DFS - Slow Browsing with Windows XP

In this blog, I have discussed the root cause of the issue where users are experiencing very slow network speed when connecting to network drive (mapping to DFS root namespace). Please note that this finding is totally based on our IT setup and it may not be the reason/cause for your issue.

Alright, we wanted to do following:
Virtualize and upgrade file servers (DFS) to Windows Server 2008 Standard R2
Virtualize and upgrade one physical 2003 domain controllers to Windows Server 2008 Standard R2

In this process, we created new domain controller and for some reason we needed to shut it down. So we shut it down. Next day, some users running Windows XP started to experience delays when they click on network drive letter (for example Z:\). It started to take time and sometime Windows Explorer stuck/hang before it populate all the folders. We tried few things together with my Manager to fix the issue but we could not solve the problem. Later, we read few articles/blogs about DFS architecture. One of the blog says, "Computers require access to the DFS service of domain controllers to enumerate trusted domains, obtain lists of available domain controllers, and to process domain namespace referral requests".

We started the new domain controller and straight way the problem solved. User is happy and back to work. We never understood why at first Windows XP did not query the old domain controller. Then, we found that computer will query all the available domain controller in forest to process domain namespace referral requests. It is strange that Windows 7 did not have this issue. Windows computer should flush its DFS cache after restart but it seems only Windows 7 is doing it correctly. There is more help available at How to troubleshoot Distributed File System Namespace access failures in Windows. Please note you can install Windows 2003 Support tools on client computer and then troubleshooting steps mentioned in above link. You can do following to flush DFS information on client computer

Dfsutil /pktflush
Dfsutil /PurgeMupCache

If you have proper explanation or our findings are wrong then please feel free to comment and direct us.


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