[Devmon] Graphs spike on reboots

[Jeremy L. <jla...@re...>]

Guys and gals

I don't know how to solve this problem.  Many of the devices I monitor with
Devmon cause some graphs to spike when the device reboots, presumably due
to counters being reset to zero.  Conventional wisdom is to use DERIVE and
set minimum to zero.  This has been done for the standard if_load devmon
templates that I'm using, and so I don't expect to see this problem.

The RRD data either side of the spike is pretty normal, and right in the
middle is a nan value.  I end up having to go back and manually "nan" the
big numbers, so that the graph scales back to normal levels.

I can't reproduce this problem every time (eg by rebooting a server).  But
it happens often enough to be a problem.

Am I doing something wrong?

Cheers
Jeremy