[rrd-users] Re: A beginners question

Jason Fesler jfesler at gigo.com
Sat Jun 9 17:36:50 MEST 2001

> Maybe you can trade in hard drive space for a performance gain.
> This of course depends highly on the details of your setup, however
> it is worth trying.

I did try this to a certain extent ages ago; haven't tried it recently.

> If you don't create graphs often, most of the current disk IO is wasted.
> Also, if your graphs are not created with a resolution that is available
> in one of the RRAs, current disk IO is wasted.

Currently I have 5 days at per-minute resolution.  After that, it
degrades.  I'm also using min/max/average storage, which, in hindsight,
is stupid (nobody is viewing anything but average).  If I had a *good* way
to clean these out I would :-).  The XML dump process is too painfull.
I should get around to marking off on my todo list the ds/rra adding in
rrdtool itself [and at the same time, allow for ds/rra removing].  Perl
scripts just aren't portable enough for more than one platform without
lots of "use this pack string if you're on this OS" magic.

> Maybe you can setup a test RRD with only one RRA.  If you use this
> RRA to graph 400 days, rrdtool will need to consolidate 400 times
> 1440 CDPs into 400 pixels.  However, you currently are doing the same
> spread out over time, even if you're not going to graph it.

The big problem, is that the data *is* refered to often - just not every
minute or 10 or 20.  Having one year-long per-minute storage of the data
is *very* slow to graph long periods of time for, which some of the people
here use to look at trends for given customers, clusters, etc.  Doing
graphs on demand was a *big* win performance wise - but I can't go so far
as to make it tedious and long for the other users to make use of.

I'll certainly try playing around with this again.  Thank you for
suggesting it.  Even if it doesn't work out for me, it might work out for
others - and the suggestion itself is certainly valid.

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