[rrd-users] graph/rrd def for small increment monitoring

A Darren Dunham ddunham at taos.com
Fri Sep 4 21:39:19 CEST 2009

On Fri, Sep 04, 2009 at 08:51:33AM -0400, Kevin P. Foote wrote:
> When graphing I now create the DEF value from my rrd and then multiply
> the value by 300 using a CDEF. This should now give me the 5 minute window 
> rather than the 1 second as mentioned before..  ??.. ??.. Yes?

You didn't change the windows, you changed the value.

Think of a spedometer.  It could be in miles-per-hour or in
feet-per-second.  But the needle is measuring the same thing.  When
muliplying by 300, you're just changing the units that you're reporting.

Changing the window would be like changing the damping on the needle.
If your fuel tank had an instantaneous level output and you were driving
on a bumpy road, then the values might be all over the place.  That's
what you get with something that happens discontinuously and a very
short sampling interval.

By increasing the step size you lose precision into when the actual
events occured, but it makes it easier to see average rates.

If just raising the value was all you needed, then good.  

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