[rrd-users] rrdtool - features ... 2nd y-axis

Karl Fischer rrd-users at ficos.de
Sat May 31 13:11:40 CEST 2008

Tobias Oetiker wrote:
> Karl,
>> I guess this is a special question for Tobias, however, any answer welcome.
>> I've searched the archives for features like a second y-axis and I found
>> that people have started working on this many years ago ...
>> Is there any particular reason it never made it into the released code?
> there was never a generic patch with a sensible interface. If you
> are interested in the second axis thing, please, before you start
> coding, come up with a configuration method and discuss it on the
> developers list ...

I'll have to think more about this ...
The grid will probably be the most difficult problem to solve.

> what is it that you try to achieve ? with integers for data storage ?

I only try to achieve to read exactly the same values back that I've put
into the database before. Especially when there are minimal changes to
very big values (eg. a few bytes in a petabyte-value) they are lost
'in the noise' in floating point but would be there in integer ...

Sometimes this can be solved by storing the same value as GAUGE and
COUNTER - to be able to retrieve minimal changes on a big value ...

At the end of the day it may not be neccessary - I just thought it
would be nice to be able to specify the datatype when creating the rrd.

It even goes further in terms of (disk) space used when you think in
the other direction:
Sometimes you need to record small ints only (e.g. because the value
never exceeds a range from 0 .. 100) - but storing doubles takes eight
times the space ...

So my wishlist would be:
* add the ability to store any common data value (8,16,32,64bit int
  and single/double floats) - to use the best match for the purpose.

I fully understand that this doesn't strike you as a very rewarding
venture - I'm just thinking about the feasability to do it myself.

Many thanks.


- Karl

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