[mrtg] Re: Basic question

[Paul C. Williamson]

MRTG does two things.  Kinda.  Also, I'm basing this on the assumption 
you are 
a) running mrtg every 5 minutes and 
b) getting your values from an OID

The OID is the data, and it is just a number as it computes it on the fly. A
  huge spike (depending on how long it happens for), may not 
even been seen, if the data just before and just after the spike is 
lower than normal.  If you are looking for detail, MRTG is not the tool fory
 ou.  You need a sniffer or some kind of probe.  Anyway, I digress.

It grabs the data, and, based on when it actually receives it, "normalizes"i
 t to make up for any differences in time.  It may have gotten it a littlel
 ater than it would have liked to.

MRTG stores the rate of change (in plain vanilla form) between time 
period x and x+y, where x is about five minutes ago, and y is now.  I 
say "about" because it could be 325 seconds since the last update, 
which will affect what number gets stored in the log.

I'm sure I've gotten something wrong, but this is close enough for what 
your asking.  If there are any glaring errors, I'm sure someone will correct 
me.

Paul

>>> Adam Waltman <AWaltman at docHarbor.net> 08/02/01 11:15AM >>>

Does mrtg, when run every 5 minutes, go out and collect a snapshot of what
is happening at 5 minute intervals and then average it or does it find out
what has been going on for the entire 5 minutes?  The reason I ask is that
if something were to spike the bandwidth in between the polling interval,
would that show up on the graphs?

Thanks,
Adam Waltman
Senior Network Engineer
docHarbor, Inc.
awaltman at docharbor.net 


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