[rrd-users] Questions about effective database parameters

[Steve Shipway]

RRA:AVERAGE:0.5:30:720
RRA:AVERAGE:0.5:60:720

You need to set the XFF (the fraction of the data which must be known for an RRA to store a value) to be much lower; in fact, you might even want to make it as near to zero as you can, maybe 1/(#dp)

So, for the above, use:

RRA:AVERAGE:0.03:30:720
RRA:AVERAGE:0.01:60:720

and even make it smaller for other RRAs.

This is a rather clever way to get around the whole data normalisation thing; by making the step size 1s you avoid normalisation, but use a tiny XFF to make sure your 1-min RRA still stores the data as posted (and averages if you get multiple samples).

Steve

Steve Shipway
University of Auckland ITS
UNIX Systems Design Lead
s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>
Ph: +64 9 373 7599 ext 86487

________________________________
From: rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch [rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] on behalf of Henrik Hegardt [henrikhegardt at hotmail.com]
Sent: Tuesday, 14 December 2010 10:59 p.m.
To: rrd-users at lists.oetiker.ch
Subject: [rrd-users] Questions about effective database parameters

Hello.
I'm writing a program to monitor a server's activities. Its about response times for services on the server. There are quite many services and most of the written data are unknowns. The response times is quite crucial and would want to have as high resolution as possible even though there are unknowns. If there's a response time I write it to the DB with 1 second interval though since there are several other services per rrd a update operation could look like 'update database.rrd 1292313983:U:U:U:U:U:U:U:0.012:U:U:U:U:U:U'. I would like to store it for atleast 6 months and thus view it over that time. I'm not interested of if there was no value, but the value itself.
I can't tell if there will be a lot of updates during a time interval or none at all which should result in some of the entries won't even get a 'U' value (most probably).
I have worked with following
rrdtool create -s 1 \
DS:ds1:GAUGE:2:0:3600 \
...
RRA:AVERAGE:0.5:30:720
RRA:AVERAGE:0.5:60:720
RRA:AVERAGE:0.5:420:720
RRA:AVERAGE:0.5:1800:720
RRA:MAX:0.5:30:720
RRA:MAX:0.5:60:720
RRA:MAX:0.5:420:720
RRA:MAX:0.5:1800:720

This didn't work, since I believe there a lot more 'U' values than 0.5 and the resolution isn't good enough and really doesn't make sense according to what I'm trying to sample.
RRA:AVERAGE:0.5:1:86400 worked but then having a rra over 6 months (6*30*86400) will result in a big db and slow rendering of images. Any ideas?

Forgive my English.


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