using iperf with small buffers

[Mitch Kutzko <mitch --at-- ncsa.uiuc.edu>]

>Date: Wed, 07 Apr 2004 14:16:21 -0400
>From: jesse butler <Jesse.Butler --at-- Sun.COM>
>Subject: using iperf with small buffers
>To: dast --at-- nlanr.net
>Reply-to: Jesse.Butler --at-- Sun.COM
>
>Hi,
>
>I'd like to use a very small window size and get a read on maximum IOPS 
>a NIC can do.  With ttcp, I can just use a small buffer size and it does 
>the trick.  I figured I'd start at 128bytes and go up from there, but 
>iperf is warning me that's too small and overriding my 128b window size 
>option:
>
># iperf -c n1sut -n 1000M -w 128   
>WARNING: TCP window size set to 128 bytes. A small window size
>will give poor performance. See the Iperf documentation.
>------------------------------------------------------------
>Client connecting to n1sut, TCP port 5001
>TCP window size: 5.70 KByte (WARNING: requested  128 Byte)
>------------------------------------------------------------
>[  4] local 10.10.1.1 port 38134 connected with 10.10.1.10 port 5001
>
>
>I understand I will not get the best throughput with this number, but as 
>I said, I'm looking for a max IOPS number with this test case.  Is there 
>a way to force iperf to use a smaller window size like this?
>
>Thanks,
>Jesse
>
>______________________________
>
> Jesse Butler
> MTS, Performance  VSP RABM
> Sun Microsystems  Burlington, MA
>
>
--
Mitch Kutzko | mitch --at-- dast.nlanr.net | mitch --at-- ncsa.uiuc.edu | 217-333-1199
http://hobbes.ncsa.uiuc.edu/