We have Jumbo-frames on our TSM/AIX servers set up. 
        
        The first thing that jumps out at me is that you have set your
MTU size to 8990. On our hosts, we set it to 9000. Just curious as to
where you got the 8990 from? Might the jumbo packets be getting
fragmented if the MTU size is not quite large enough?

root:># netstat -ir
Name  Mtu   Network     Address            Ipkts Ierrs    Opkts Oerrs
Coll
en3   9000  link#3      0.4.xx.xx.xx.xx   613019983     0 185530524
2     0
en3   9000  192.18.16   tsmhostX          613019983     0 185530524
2     0

Ben 

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Miller, Ryan
Sent: Wednesday, March 23, 2005 10:05 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: TCP settings for Jumbo frames

Here's a question from one of my cohorts, since this is our first try at
this, I thought I would see if I could get any input from anyone else
doing this.
 
We have been testing jumbo frames(8990) using TSM on an AIX client. The
base line test with MTU of 1500 moved 22G in 44 minutes. Changing the
MTU to 8990 and the TCP receive and send buffer sizes on both the
mainframe and AIX client to 256K, the same 22G of data takes 1 hour and
40 minutes.

Also the largest input packet size is 8192, not 8940. Are their any tcp
parameters to se on the client that would help with the jumbo frame
transfer time?

 

Ryan Miller 
 

 


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