[mrtg] Re: Best box and OS to use

Greg.Volk at edwardjones.com Greg.Volk at edwardjones.com
Thu Aug 22 15:42:30 MEST 2002

}Currently I am running on a Celeron 400 with a 3.2gb HDD and 
}64mb memory
}running FreeBsd 4.0.  With the amount of stuff I am watching, 
}I think this
}thing is struggling.  
}What recommendations can the list give me as far as what OS is 
}most stable
}and commonly used etc for mrtg?
}What kind of hardware is being run?

I run 8299 five minute targets on a dual-proc Sun 220R with 2GB of 
memory, and I'm terribly unimpressed. For polling robustness, and 
timing reasons I have the targets spread across 59 daemons thus I do 
not use the Forks: directive. Nonetheless, it gets the job done. On 
average the load on the box (from the uptime command) is only .48 (15 
min) for the last 24 hours. By far, the biggest performance problem I 
have with this box is dynamic graph generation via 14all.cgi. The procs 
are only 450Mhz each, and the machine really drags when you ask it for 
a big index of 50+ graphs.

}I have a 733 desktop PC, 20gb and just put 384mb in it I could 
}dedicate to
}this for now.  Would this make a big difference for me?  I am getting
}emails/reports of lock files since I added my last router with 
}about 450 sub
}interfaces and I think it is because it can't finish polling 
}it in time.  I
}have had no luck with getting the graphical interface on 
}Freebsd, but with
}an install of RH71 and OpenLinux 3.1 being no problem.

How many interfaces total do you want the box to be able to poll every 
five minutes?

How many concurrent copies of mrtg (daemons) do you want to run? The 
maximum number of daemons is tied to how much ram you have. As I said 
above, I have 2GB RAM, and run 59 daemons. That's about all I can do. 
According to top my memory stats are:
Memory: 2048M real, 227M free, 358M swap in use, 3306M swap free
I run about 150 targets per daemon. This seems to work well for me as I 
never see gaps due to overly-long poll cycles in my graphs.

IMHO high-clock x86 systems are best for graph generation. For 
instance, I have played with 14all.cgi on a dual proc AMD 1.4Ghz box 
and it pumped out graphs just about as fast as my web browser could 
display them. I don't know how well an x86 box would scale for big-time 
polling though (8299 five minute targets for instance). My suspicion is 
that it would do fine as long as there is enough memory free, and the 
polls are spread out among a good number of daemons. I tried forking, 
and decided that I liked multiple daemons better for the reasons listed 
in http://www.ee.ethz.ch/~slist/mrtg/msg14856.html

As for an operating system. Wellll...I'm a slackware (gasp!) linux 
person. ;) But I don't think it makes much difference. My Sun 220R runs 
Solaris 2.6. I've never run mrtg on top of windows, so I can't really 
say whether or not the performance is better or worse than running a 
different operating system on the same x86 hardware. I would be very 
interested to see the results of some comparison testing though.

There are lots of things to consider when tuning a big installation of 

Polling latency - if a bunch of your targets are 100ms away, then you 
may exceed the poll cycle time. Fewer targets per daemon, or more forks 
might be necessary.

Available CPU and RAM resources - for the reasons listed above.

I/O subsystem performance - I haven't had too much trouble from this 
yet, but do keep in mind that in a big installation mrtg does lots of 
reads and writes on many, many individual RRD files.

Number of users that will request dynamic graphs at one time - When 
there is a significant  network issue around here my 220R gets 
clobbered with graph requests. I've seen the load spike up to 20, all 
due copies of 14all.cgi.

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