Problem with DFS when enumerating large folders

Question

Hi,
In our organization we have DFS in place. We don't use DFS-r replication. The DFS roots are hosted on 3 2012R2 domain controllers and we have 2 domain based namespaces (windows 2000 mode). We have a lot of issues when users/applications/servers are trying
to open folders with lots of files in them (typically 10000+). When this happens DFS hangs organization wide. This causes a lot of problems for back-end applications which are constantly moving around files to different front-end systems. Most of them
get exceptions resulting in a manual restart. Since our organization is running 24/24, 7/7, this is very ennoying. Especially for engineers who have to get up at night to restart those services.
All user folders/mapped network disks are using DFS to access the file server. We have more then 2000 employees accessing a DFS namespace. At the time the issue occurs, they also experience problems accessing their data. 
When the issues occur, we have no problems accessing the targets themselves, so we can exclude file server issues. We use a third party appliance as DNS server, but this also works as should at the time the issue occurs. The only way to resolve our issue
that we have found so far is to clean out those folders, or when that's not possible, exlude them from the DFS namespace.
We thought upgrading our DC's from 2003 to 2012R2 would resolve the issue but that didn't do it. Is this a known issue and is there another workaround/fix? Also, is there a way to find out which target caused
DFS to hang? We have already done a lot of troubleshooting with articles we found on the net but nothing seems to be wrong with our DFS setup/AD/DNS. We also opened serveral cases with MSFT but after the network trace analysis they always conclude there's
nothing wrong.
Thanks in advance! 

Answer 1

Hi,
Distributed File System (DFS) currently has a size recommendation of 5000 folders with a target in a domain-based namespace. It belongs to Windows Server 2000 DFSN and not to Windows Server 2008. You could create a domain namespace in “Windows Server 2008 mode”
to create more than 5000 folder. 
When the number of links exceeds the recommended limit, you might experience performance degradation when making changes to the DFS configuration.
To reduce this problem, you could add more DFS Namespace server to spread the request to more servers. 
For more detailed information, please refer to the article below:
Reviewing DFS Size Recommendations
http://technet.microsoft.com/en-us/library/cc776068(v=ws.10).aspx
DFSN PERFORMANCE, WHERE ARE YOU?
http://marco-difeo.de/2014/01/16/dfsn-performance-where-are-you/
Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Best Regards,
Mandy
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