[mrtg] Intermittent Graphs

[Alex van den Bogaerdt]

On Sat, Feb 02, 2008 at 08:55:46AM -0500, Darren.Terry at cox.com wrote:

>      This past week I migrated a very, very large MRTG installation to
> new servers and updated software. Everything went well with the
> relocation with the exception of one group of hardware. The group of
> CMTS systems that I am graphing aren't graphing correctly. They have
> graphs which are very intermittent. They look like saw blades. I believe
> the reason that they are so intermittent is that the poll isn't
> finishing before the next one needs to start. So, I am receiving the
> lock file error in email. However, this doesn't make sense. I upgraded
> to servers that are LEAST five times stronger. In addition to this,
> according to the FAQ on the MRTG site, the graphs should be populated
> with the previous data rather than zero.
> 
> 	If anyone has any ideas about how to speed up the poll or
> anything else that might help, I am all ears (or eyes?)!! 

Lock file errors, meaning it takes too much time to finish one round,
and the next one is started before the prevous one has finished.

Perhaps two polling periods is enough for those counters to wrap
around, similarly to the infamous 114Kbps at 5-minute intervals.

Things to try:
* increase IO speed
* use HC counters
* run multiple MRTG instances parallel

A temporary workaround may be to increase the polling interval from
five to six minutes (or maybe seven), but not to ten as that would
most likely will result in more, not less, saw blade-looking.

HTH
Alex