Ryan,

In order to do performance tuning accurately I would need a whole lot
more information.  Also, I am an AIX guy so I can't help on the
mainframe side.  So I will just list a few things for you to look at and
see if this will help.  First of all in order to use Jumbo Frames all
devices along the entire path most support Jumbo Frames as well, i.e.
switch, routers, sending and receiving systems.  The majority of the
time my customers have problems with this is when the router or switch
either isn't enabled for Jumbos or just doesn't support item.  Now if
that isn't the problem there are still a few network parameters that
could cost you performance.  If you increase the tcp send and receive
buffers you must also increase the "sb_max" (this is on the AIX side,
not sure what you do on the mainframe) to be a value about 1.25X that of
the largest send/receive buffer.  Another thing to look at is if you
increase these socket buffers above 64K then you must enable RFC1323 or
else it still only uses 64K buffers regardless of your settings.

also, I might point out that your initial numbers of 22GB in 44 minutes
(8.33MB/sec) is pretty slow for a GigE connection.  Another issue might
be a file I/O problem either reading or writing the data at the sending
and receiving ends respectfully.

Let us know how you progress.

--
Regards,
Mark D. Rodriguez
President MDR Consulting, Inc.

===============================================================================
MDR Consulting
The very best in Technical Training and Consulting.
IBM Advanced Business Partner
SAIR Linux and GNU Authorized Center for Education
IBM Certified Advanced Technical Expert, CATE
AIX Support and Performance Tuning, RS6000 SP, TSM/ADSM and Linux
Red Hat Certified Engineer, RHCE
===============================================================================



Miller, Ryan wrote:

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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