Re: using iperf with small buffers
> >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?
This looks like the OS imposing a minimum window size. Iperf doesn't impose
any limit, it does however report what the OS gave it if that differs from
what was requested.
Jon
--
Jon Dugan | Senior Network Engineer, NCSA Network Research
jdugan --at-- ncsa.uiuc.edu | 269 CAB, 605 E Springfield, Champaign, IL 61820
217-244-7715 | http://www.ncsa.uiuc.edu/~jdugan/