<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2900.2769" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT face=Arial>Joachim wrote:</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>>I/O is a complex topic, and a single number rarely
tells you enough if you want <BR>>to analyze what's going on. For this
purpose, IOzone is very powerful. But <BR>>again, it does only run on a
single node (although can fork processes/threads to <BR>>perform concurrent
operations). You could start it on multiple nodes, but then <BR>>the I/O is
not synchronized, which may or may not what you want to do.<BR><BR>>--
<BR>>Joachim Worringen - NEC C&C research lab St.Augustin<BR>>fon
+49-2241-9252.20 - fax .99 - <A
href="http://www.ccrl-nece.de">http://www.ccrl-nece.de</A></FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial><FONT size=2> Iozone is able to run
across multiple nodes. See the -+m and -t options.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> It knows how to use rsh
and can also use any remote execution</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> method by simply setting
the environmental variable RSH to </FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> whatever works for you.
Example: RSH=ssh ; export RSH</FONT></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial><FONT size=2> When Iozone is running
across multiple nodes the I/O and </FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> testing IS synchronized
via a barrier mechanism. Also, </FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> straggler effects are
minimized via the stonewalling technique</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> inside of Iozone.
The technique goes like this:</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT size=2> Master Iozone:
starts remote copies on all nodes.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> Client Iozone: startup,
and reach barrier, then wait for go from master.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> Master Iozone: Sees all
remote copies check-in at the barrier, and</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT
size=2> sends
message telling them to begin testing.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT size=2> First client to finish:
Sends message to master, telling master, I'm done.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> Master: Sends message to
all remaining instances of Iozone, telling</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2>
them to stop measurement, as the parallel
region has ended.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> Remaining clients report
results to master, and exit.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2> Master totals results and
reports results to user.</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2></FONT></FONT> </DIV>
<DIV><FONT face=Arial><FONT size=2>Enjoy,</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2>Don Capps</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2>capps _at_ iozone _dot_
org</FONT></FONT></DIV>
<DIV><FONT face=Arial><FONT size=2></FONT> </DIV>
<DIV><BR><BR></DIV><!--endarticle--></FONT></BODY></HTML>