[mrtg] linux performance

Perry, Duane PerryD at missouri.edu
Tue Oct 24 14:45:30 MEST 2006

I may be trying to do more than MRTG was ever designed to do but right
now I am polling about 25,000 interfaces with a Dell 2850 running Red
Hat Linux Enterprise rel 4.  It is actually working but barely finishes
processing the rrd files in the 5 minute polling cycle.  We ordered a
new Dell 2950 with Dual Core cpu and I expected much faster processing.
The reality is that it does not complete much faster than the old box.
I had consolidated all of my Targets into one large config file for
polling and keep separate config files for display.  I have been using a
"fork" setting of 16.  I issue "/usr/bin/mrtg /usr/local/cfg/targ1.cfg"
from a crontab.  The polling part seems to go quite quickly (~30
seconds) but writing the results to the rrd files is taking as long as 3
or 4 minutes.  I tried splitting the config up into multiple parts and
running them concurrently in the background but it does not seem to
help.  I suspect that some module called by the mrtg script is single
threading the process and more processes just leads to more swapping and
is actually LESS efficient.  

Does anyone have any suggestions on ways to speed up the processing?  Is
anyone out there monitoring an enterprise this large?  Gathering
IfInOctets and IfOutOctets for every port on campus is 90% of the load.
I also monitor firewall connections, wireless connections, modems and a
few other miscellaneous stats.  I would like to continue adding other
graphs as we identify MIBS that will help us monitor network health.  I
thought throwing massive processing power at the problem would give me
some room for growth but right now I don't feel like I have much of a


Duane Perry

University of Missouri

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