[rrd-developers] interleaving RRD files, RRDfs perhaps?

Daniel.Pocock at barclayscapital.com Daniel.Pocock at barclayscapital.com
Fri Oct 3 10:24:23 CEST 2008

 > Normally the filesystem should be able to take care of quite 
> a lot of otimization duties as long as you present it with a 
> siutable workload. So maybe there is some low hanging fruit 
> to be harvested by looking at when and in what order 
> rrdcached does its updates and also maybe how they are 
> performed by the rrd update code, without gowing to a raw device ...

I'm certainly studying that as well - the interleaving would work at a
lower level than rrdcached, and would allow the block-level caching
systems to have a higher chance of success.
> I am pretty sure though that you can esily devise a much more 
> performant system if you start limiting the way data can be 
> deliverd (eg all rrds look the same)

That is certainly the case with some applications, e.g. Ganglia
> Looking at the existing code, did you investigate creating 
> rrd files with a LOT of DSes ?

Yes, that seems like a possibility - but many applications, such as
Ganglia, create new RRDs on the fly.  Therefore, there would need to be
some way of creating an optimal number of empty DSes in advance, and
then mapping them to application-specific names when they are needed.
This logic could be implemented in the app or rrdtool.

Implementing within rrdtool in a way that preserves the existing rrdtool
API seems to be desirable - perhaps the different operating mode could
be enabled by some kind of environment variable and/or an rrdtool
configuration file in /etc?

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