[mrtg] Using 95th percentile with mrtg configs

Steve Shipway s.shipway at auckland.ac.nz
Wed Jul 14 23:52:37 CEST 2010

Routers2 allows you to selectively turn off calculation of 95th Percentile and Totals on a per-target basis using

routers.cgi*Options[]: nopercentile
routers.cgi*Options[]: nototal

You need to first globally enable the total/percentile module in the routers2.conf, though, by using the directive:

percentile = yes

There is not currently an option to selectively turn it on, because of the way the calculation module is linked into the code, but you can use a global default (as in your example) to globally disable and then selectively enable if you want. Originally this module was computationally expensive, but currently this additional loading is minimal due to improvements in Routers2 and RRDTool.

The percentile calculations use the best RRA available; therefore you lose accuracy on higher granularity (eg, monthly graphs).  You can fix this by using the RRDRowCount[] directive, or RRDRowCount2h[] (if you have MRTG 2.16.4 or better) to set the row count to 9600 or better (this only affects NEW RRD files, with existing RRD files you'll need to use rrdtune to expand the first RRA to have the same effect)


From: Mersberger, Robert [mailto:robert.mersberger at goldenliving.com]

I am looking to try this but noticed that it is a variable in routers2.conf that need to be turned on. If I under stand this correctly this will have a global effect on all my current configs, which at the present is something I don't want. Is there a way to turn this option on in cfgmaker ?  Would it go here ? (--global="routers.cgi*Options[_]: scaled percentile")  I believe that this can be used to turn it off if it is on in the .conf file.   This is how I understood it from reading your first edition of Using MRTG with RRDtool and Routers2?

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