Why is FTP to localhost slower on Solaris2.9 than 2.8?

From: Alek O. Komarnitsky (N-CSC) (alek@ast.lmco.com)
Date: Thu May 08 2003 - 09:55:32 EDT


We have about a dozen Sun280R's here on site and have been doing
some misc. testing for GigE - as an aside, I've seen consistant
60+ MBytes/second to/from dual-CPU machiens - smoking!!!

One thing I noticed was a very consistant different between FTP's
to localhost. I.e. I've been using the following as a poor-man's
single-thread benchmark test:
   1. Create at least 100 MByte file in /tmp which is swapfs
   2. ftp to localhost (yes, there is a 127.0.0.1 entry in /etc/hosts)
   3. Ensure in binary mode
   4 put FILENAME /dev/null (i.e. just dump into the bit bucket)
   5. Repeat several to insure source file is RAM resident & consistant results
My thinking is that this is the absolute upper limit I could ever see
from the machine/network stack ... and the data shouldn't even go out
on the wires.

The strang thing I noticed is that on ALL of my 280R's (identical
build procedure) running Solaris2.8, I average between 110-140 MBytes/sec.
However, on ALL of my Solaris2.9 machines, I average 50-70 MBytes/sec.

I realize that for production, we won't be FTP'ing to localhost! ;-)
But I was puzzled by these results and wonder if anyone can shed any
light on why Solaris2.9 is consistantly slower than Solaris 2.8 on this.
I'll summerize to the list of course.

Thanx,
alek
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