I have a quad processor vmware instance running Windows 2003 and 1gb ethernet. I'm comparing serving the exact same heavy .NET 2.0 content from the local hard drive versus serving it from a UNC drive.
If I use WCAT to load it down, I see about a 40% reduction in transactions/sec while serving from the UNC. Processor time barely moves from 45% and the NIC sits around 40% either way. I don't see any significant memory loading either way. Context Switches/Transaction, though, more than doubles when serving from the UNC. Pathlengths more than double as well, but I believe that's just an expression of the effect of context switching.
All told, it looks like the bottleneck is processor switching while waiting on content from the UNC share. Is my experience about the norm? Is there some mitigation I might try?
I twiddled HKLM\System\CurrentControlSet\Services\LanmanWorkstation\Parameters\MaxCmds a little bit per http://technet.microsoft.com/en-us/library/dd296694(WS.10).aspx, but to no obvious effect. I kind of doubt my problem is lack of connections, but rather just the act of switching from thread to thread while waiting on data.