[rrd-users] Re: Spikes

[Tobias Oetiker]

Today you sent me mail regarding [rrd-users] Re: Spikes:

*> Daniel Rinehart wrote:
*> > 
*> > 	I don't know if this is related but I've also been seeing some
*> > strange spikes in Octet readings I've been getting from one of my Cisco
*> > Catalyst 8510 ATM switches. I'm still at the initial stages of debugging this
*> > problem but this is what I have found so far.
*> > 	Values as seen by my Perl script doing the collection before
*> > passing them off to RRD:
*> >                   'atm_out' => 3438905,
*> >                   'atm_out' => 3457190,
*> >                   'atm_out' => 1484,
*> >                   'atm_out' => 19875,
*> > 
*> > 	Another sample:
*> >                   'atm_out' => 3421998,
*> >                   'atm_out' => 3452632,
*> >                   'atm_out' => 26394,
*> >                   'atm_out' => 58936,
*> > 
*> > 	Maybe, I'm missing something, but that sure looks like an odd wrap
*> > point to me.	
*> > 
*> 
*> This looks like a reset to me, not a wrap.  Not sure about the 8510 but
*> on the 5500 series the snmp counters will reset too when you issue a
*> clear counters command from the prompt.
*> Unfortunately the snmp uptime is *not* reset when doing this ...
*> 
*> >From 3452632 to 26394 should be seen as a wrap at 2^32 and therefore the
*> delta should be 4291541058. That's 4,291,541,058.  Divided by 300 (5min)
*> you should get a spike with size 14M.  Correct?

we might think of some sensibility check here: if a wrap occurs the data
calculated by the wrap around code may only differ from the last value
logged by a certain percentage ... otherwhise it goes *unknown*

cheers
tobi
*> 
*> Regards,
*> 

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