A couple questions...  When the drive mapping lost,  what exactly do you see?  No mapped drive?  a red "x"? Something else?  Can the share be accessed via UNC path?  Are you front ending this with a DFS server?

Yes, there is no red X nothing and they dont exist in explorer at all. Shares can be accessed via UNC path and yes, there is DFS. It seems more like issue not from storage side

Is the drive mapped via group policy or a log on script? 

Try this map a second drive in the exact same manner,  but make right to isilon and not the DFS server.  see if that helps..

Mapped using a log on script

exact same manner ? what are you referring to

Hi Damal,

My first guess is a problem with DNS-Entries. When a network drive dissolves usually the TTL for this DNS leads to a loss of connectivity. Do you use WINS? How do clients resolve your DFS-Name to the smartconnect-Zone?

Here is a (rather old) article describing a brief walktrough how to solve kerberos authentication problem:

Troubleshooting Kerberos Authentication problems – Name resolution issues - Ask the Directory Services Team - Site Home …

Check out this document: https://emc--c.na5.visual.force.com/apex/KB_HowTo?id=kA0700000004Jqi

I had to correct our AD-Settings as the Isilon struggles with large security token sizes. This often happend's when you use a lot of delegation or the member is part of too many AD groups.

Did you do a network trace on the affected client? It helps a lot to see the difference between a failed connection and a working connection.

PS: Is there any other OS than Windows 7?

Ingo

In your login script map a 2nd drive... this time directly to Isilon and not the DFS server.   See if that drive goes away also,  of if its limited to the DFS drive disappearing.

That was the issue when we were seeing this problem.

That article isn't pulling up for me.  Can you share the contents?

Is it resolved now?

Yes Mark