Windows share: The specified network name is no longer available

We've got an EMC NX4 SAN box serving a CIFS share to a number of Windows Server 2008 R2 app servers. The app servers are using the CIFS share to serve lots of image files (~2500 ops/sec on the share), however neither the SAN nor the app servers are showing any obvious signs of stress.

Once in a while an app server will, apparently all of a sudden, drop the connection to the SAN. Any .NET code trying to serve a file from the SAN fails with:

System.IO.IOException: The specified network name is no longer available

If I RDP to the app server and try to access "\san-name" through explorer, I get the same error. All other app servers can access it just fine. I can also access "\ip-of-san" just perfectly, pinging works as well.

A reboot of the app server fixes the issue, but that's a somewhat drastic measure to the problem, given that it seems like the SAN is working fine and the computer can access it - it just looks like the "\san-name" access has barfed up.

This has happened to two different app servers during the last week, so I don't suspect a single app server of being the cause. Ignoring the cause for now - how would I restore the "\san-name" connection without rebooting the machine? And can I somehow query what went wrong?

Event logs shows nothing (besides related ASP.NET errors caused by the issue), neither on app servers nor on the SAN.

Update:
Based on the suggestions I'll try a restart of the Workstation service the next time and see if that helps the issue. Definitely not a fix, but way faster to do than to reboot the whole machine as I've currently been doing. Any way to query the status of the connections that the Workstation service maintains?

Update 2:
Confirmed that restarting the Workstation service "fixes" the issue. Next step is to try the reg change to heighten the MaxCmds value. Won't be able to confirm whether it's the issue, can only assume if it runs for a lengthy period without issues.

Solution 1:

This sounds like it's the MaxCmds have run out. Here are two good articles about that: here and here.

Here's now to change it. Create a file called update.reg and place the following in it:

Windows Registry Editor Version 5.00 

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanworkstation\parameters] 
"MaxCmds"=dword:00000800 

Save and then double click and accept the prompt. A reboot is required.

Solution 2:

maybe restart the workstation service on the app server!