[rrd-users] Re: made mistake during creating rrd

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Jun 28 16:48:09 MEST 2005

On Tue, Jun 28, 2005 at 03:37:54PM +0200, Andreas Ihl wrote:

> > Do the updates, oldest first.  After doing this, your new RRD contains
> > the same data; except for the resolution which *seems* to be better.
> > (it isn't, not yet).
> do you mean the following behavior?

No. I mean one single update fills 60 rows.  It looks as if the resolution
is increased by a factor of 60 but since the 60 rows are the same, the
resolution equals that of the original.

Only after a while, when new updates make it in this RRA, the situation

> also in the 1440 section but only until 2005-05-28:

> any idea what i am doing wrong?

Not really.  Obviously something happens around this date.  Examine your
input data, look for things that may go wrong.  One thing may have happened:
maybe you didn't strip the input well enough.

You must not include all of the RRA with 86400 PDPs per row. You should
skip timestamps that are already included in other RRAs.  Similar for the
other RRAs, you should only include a line if this interval is not included
by other RRAs.  If the RRA covering one PDP per CDP ends at 2005-06-28 00:00,
you should not include any CDP from the other RRAs which end time is later
or equal than 2005-06-28 00:00.  You already have input for that time, at
the best quality, so skip it from the other RRAs.

To debug in case the previous paragraph is already covered:

Take a couple of updates and compute by other means what RRDtool should
do with the data.  Your timestamps will be at whole multiples of 60 seconds.
Each time an update occurs, the corresponding CDP will be set as well as
the previous CDPs not yet done.

2005-06-28 14:00   this update will set the rate for all intervals upto 14:00
                   including the one from 2005-06-28 13:59...2005-06-28 14:00
2005-06-28 14:15   this update will set 2005-06-28 14:00...2005-06-28 14:01
                   upto 2005-06-28 14:14...2005-06-28 14:15
2005-06-28 14:30   15 intervals: 2005-06-28 14:15...2005-06-28 14:16 to
                   2005-06-28 14:29...2005-06-28 14:30
2005-06-28 14:45   and so on.

For the RRA covering 24 hours per row (1440 PDPs per CDP), you should use
all PDPs generated ending _after_ 2005-06-27 02:00 upto and including the
one ending _before_or_at_ 2005-06-28 02:00.  Depending on the available
resolution, this may mean 1440 rows.  Multiply each rate by the amount of
time covered (the difference between the previous update and this one),
add up all of those numbers, divide by 86400.  The resulting rate should
appear in the RRA at time slot 2005-06-28 02:00.

I notice you are doing MIN and MAX as well.  If you also have that in
your original RRD, don't use them for this conversion.  If you really
value those MINs and MAXes, perhaps you should examine the format of
an RRD dump and transform an existing dump into a new one in the format
you want it to be:

Your original RRA:
      1114560000  avg1a avg2b avg3b
      1119744000  avg1b avg2b avg3b
      1114560000  min1a min2a min3b
      1119744000  min1b min2b min3b
   and so on

Your new RRA:
      1114560000  avg1a avg2a avg3a
      1114646400  avg1b avg2b avg3b
      1114732800  avg1b avg2b avg3b
      1114819200  avg1b avg2b avg3b
      [and so on]
      1119744000  avg1b avg2b avg3b
      1114560000  min1a min2a min3a
      1114646400  min1b min2b min3b
      1114732800  min1b min2b min3b
      [and so on]
      1119744000  min1b min2b min3b
   and so on

Make sure you cover exactly the right amount of time when doing this
(meaning: exactly the right amount of rows).


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