[rrd-users] Re: Graphs over several years without specifying end time?

[Alex van den Bogaerdt]

Simon Josefsson wrote:
> 
> I want to monitor things over a long time and I'm worried about
> running past the end time of a RRD.
> 
> Should I simply make the RRD end in 50 years?  Is there a more elegant
> solution?

There's only one solution and that is to *start* it just before
the first statistics that you're going to use.  Any less and you
will lose data, any more is just pure wasting resources.

> Currently I'm extracting all data from a SQL database and run rrd
> create+update's+graph each time I want a graph, specifying new
> start/end times.

This is not very elegant but if you need to alter your data after
you used them for graphing it's probably the only solution.
If you don't need to do so, just update the RRA with the new entries
from the SQL database.  The rest of this mail isn't valid in that
case.

You can find out what your earliest data entry is (using SQL) and
what the current datetime is.  The amount of time involved has
to fit in one graph so the next thing to find out is what the
amount of time per pixel will be.  Set this as the step time.
Each CDP in the RRA should then be build from one PDP, run update
as you do now and graph the result.  This way you should AFAIK get
the best performance with the least disk space used.

The reason for all this is that the data needs to be in a certain
resolution when graphing.  It doesn't help to have a better resolution
in the RRA as this gets consolidated anyway, it is therefore better
to do this at the update stage.

cheers
Alex

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