Slow opening of files on DFS

Question

I built a Windows 2008 R2 SP1 VM server, installed DFS and created a namespace.  I then added a folder and moved data from a CIFS share that was near capacity to free up space.  Everything I have mentioned so far was just to alevaite the fact that
the CIFS share was almost full.  I built this server as a temp solution until I got the hardware in to build a new dedicated server for DFS/Storage.  I have built the new Windows 2008 R2 SP1 physical server and also made it a namespace server. 
The performance of this server is
Phenomenal.  All the storage is local to the box as I am trying to consolidate all the shares around the network.  I replicated the share from the temp server to the new server and removed the referral from the old server.  I then copied
a few new shares over to the new server and added a folder for each (no replication for these).  I then moved the home drives to DFS.  Everything has been going well for a few weeks.  Yesterday users started reporting slow opening of files,
specifically Excel and Word but I noticed PDFs opened slow also.  This issue currently only affects Windows 7 users but only a handful.  The nic, cpu and memory on the physical server have very low utilization.  I have been unable to isolate
the exact issue but if I point the users to the
\\server\share, the files open VERY fast.  I did notice that when I right-clicked on a mapped DFS drive, the DFS tab showed the status as Unreachable.  I flushed the cache on the client and it went to OKay but file opening is still slow. 
After some testing it appears to take almost exactly 50 seconds to open a file every time.  I am going to be away from the office for a few days so I went ahead and changed all the DFS mapped drives to point to
\\server\share for now as I will not get it resolved before i leave.   I also scoured the internet for resolutions and looked at all the related topics that were presented when I typed the title of this thread. 
I installed DFSUTIL on a few of the Windows 7 computers experiencing the slowness and the referrals look good.  Every test through DFSUTIL looks fine.
Any recommendations would be greatly appreciated.
Thanks

Answer 1

I found the self-inflicted issue.  I have a dedicated DFS NameSpace server with 66TB of storage.  The drive that has this attached storage has a folder I created call DFS where all the new DFS folders are pointed.  At this point I should have
reviewed the drive permissions closer.  The default permissions on the drive includes the local USERS group which has special permissions.  The first few shares I moved over already had authenticated users - Modify so all was well.  I then moved
the home folders over and relaized that the local users allowed everyone to view everyone elses home drive.  In a kneejerk reaction I removed the USERS group from the root of the drive which no longer allowed users to access the
\\domain.com\namespace because the DFSRoots folder is also on the same drive.  I guess that since they didnt have access they eventually defaulted back to
\\servername\namespace which caused the delay???
I added the permissions back under the namespace folder and only applied to that folder.  Users can now access the namespace quickly.  At this point I am not sure what the permissions should be for the root drive.  So now my question is:
1.  If I am doing to dedicate a drive to DFS, what should the root permissions be on the drive?  The drive will contain a folder E:\DFS as a root folder for all the shares and another folder named E:\DFSRoots (created by DFS with the default drive
changed from C: to E:) which will obvioulsy hold the namespace.
2.  If a user would lose permissions to the dfs namespace (as they did in my case) how were they eventually able to access the file after the 50 second delay?
Thanks