[NCLUG] Networking Issue

[Michael Coffman]

I don't do networking and our corporate networking group has been cut so 
thin, they don't do much networking anymore either :(

This is not a linux problem, but I know there are folks on this list that 
have deep networking experience.  I'll try to describe the problem as best 
as I can in ascii.

*NA = NetApp
*CS = Compute Server

#----  A
NA -10g-> hp5412(a) -10g mesh-> hp5412(b) -1g-> CS
NA -10g-> hp5412(a) -10g mesh-> hp5412(b) -4g trunk-> hp2500 -1g-> CS

o The read path to the compute server is very slow 20-30MB/s
o The write path to the NetApp is close to wire speed 110-130MB/s
o The hp5412(b) switch is having thousands of discards at the port to the
   CS system
o Enabling flow control on all the switches on the mesh almost
   completely eliminates the discards and increases read performance, but
   hurts write performance
o Reversing the flow above does not have the same performance problems
o Reversing the flow above does not cause discards on hp5412(a)

#---- B
NA -10g-> hp5412(a) -10g mesh-> hp5412(b) -10g-> hp5800 -1g-> CS

o The above scenario has no performance issues.
o Still seeing discardson hp5412(b) due to other traffic on the switch

#---- C
NA -10g-> hp5412(a) -1g-> CS
NA -10g-> hp5412(a) -1g-> hp2500 -1g-> CS

o The above scenario works fine.
o The hp5412(a) is not seeing the discards that hp5412(b) does.

Any ideas on how to go about trouble shooting this?

I am not looking for free answers to this problem here, I would be glad to 
talk to someone about doing some network consulting.  Also any pointers to 
a networking consultant/guru would be greatly appreciated.

Thanks.
-MichaelC