'Exact values for an interval' and 'exact value at a time' are different things.
To store the exact value you want with no averaging just store it on the
step-size interval boundary, rrdtool won't average those. ie: binary data is
no problem 0/1 if stored on the interval.
________________________________
From: Tobi Oetiker <[email protected]>
To: Travis Griggs <[email protected]>
Cc: "[email protected]" <[email protected]>
Sent: Monday, October 15, 2012 2:36 PM
Subject: Re: [rrd-users] Newcomer's RRD design dillemmas
On 15.10.2012, at 16:16, Travis Griggs <[email protected]> wrote:
> A friend suggested I take a look at RRDTools for a problem I'm dealing with.
> We're monitoring a number of custom devices in the agricultural world. We did
> a naive "just store the telemetry in a database" thing originally. It was a
> quick prototype that was contracted out. We quickly ran out of room. Even
> telemetry at a trickle adds up fast. Since it was a Smalltalk database, I
> built a custom edge triggered data collector that radically reduced the data,
> since we mostly care about changes and when the occur. But that's not a long
> term solution for us. So I'm looking at RRD. After a couple hours
> reading/growsing/playing, I'm left with the following questions:
>
> 1) Each device we keep track of telemetry for, has a couple of different
> measures. I've concluded that we shouldn't try to store dissimilar data types
> in the same rrd file, even with separate RRAs. For example, we keep track of
> battery voltage, and an hour's average is plenty high enough resolution for
> us, but we also keep track of hydraulic pressures, and we'd really like to
> have these at a minute resolution. It seems I'd be best served by having
> different rrd's for these, one with a battery voltage DS, and the other with
> pressure DS's.
>
yes separate rrds with different step sizes.
> 2) While some of our data is scalar data (pressure, voltage, signal
> strength), others is just binary status. Is it on or off? I'm not convinced
> that binary status is easy to do with RRD, without playing some pretending
> games. For most of the binary values, we tend to want to record any change in
> them at a minutes resolution (that's how often the telemetry can come in).
> But we don't ever want to "average them away" or anything. Changes are
> usually infrequent (at most once per every couple of hours), but we want to
> know exactly when they happened and not "lose" any of them, at least for a
> given backwards time interval, such as a growing season (e.g. ~5 months).
> Should I be looking at doing an alternative storage scheme for these, rrd's
> for the scalar info, and something different for the edge triggered binaries?
>
if you need exact time (events) you should store them separately
but if you wat to know the percentage the switch was off or on you clud setup a
rather lowres rrd. if the changes are realy infrequent you could even calcilate
when thy happene from the ratio
hth
tobi
> Thanks for any help/direction/feedback/tips.
>
> --
> Travis Griggs
> "A vital ingredient of success is not knowing that what you're attempting
> can't be done." -Terry Pratchett
>
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> [email protected]
> https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
>
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