[collectd] Performance of the rrdtool plugin

[Kun Richárd]

Hi, 

> so you're doing / trying to do either 143 (10 second interval) or 71 (20
> second interval) updates per second. In my experience this is about as
> much as you can get to disk with the random writes librrd performs. The
> transfer rate is also in the range I'd expect.

Thanks, it seems to be a good idea, the parameter CacheTimeout with the
value of 120 reduced the load average in the last 10 minutes to 0.3-0.4. I'm
not fully satisfied with this, but temporarily good enough:)

> Fortunately for you, all your RRD files will fit into memory, so you
> should be able to gain some performance by telling the operating system
> to keep writes in memory for a while. Details on operating system and
> file system tuning can be found in the RRDTool wiki at
> <http://oss.oetiker.ch/rrdtool-trac/wiki/TuningRRD>.
> Especially mounting with the `noatime' and `nodiratime' options has
> proven to be easy and effective.
> 
> If those measures don't suffice, you can check out the rrdtool plugin's
> own performance features. As Alessandro has pointed out, setting
> `CacheTimeout' to a minute or two can greatly reduce the IO load on your
> system. The entire concept of collectd's rrdtool plugin is explained in
> great detail in the ``Inside the rrdtool plugin'' article:
> <http://collectd.org/documentation/inside_rrdtool.shtml>

I would like to read this manuals and I hope I can share my experiences with
the list next week.

Thanks!

--
 Ricsi
 kun.richard at kirzen.hu