[rrd-developers] Re: rrdsplit and perl 5.8 module for windows

[Stanislav Sinyagin]

'morning everyone, 

--- Hans-Peter Werner <hp at lipfish.org> wrote:
> xml as intermediate-format is what i was thinking of at first. but it has a
> severe drawback. xml-files are getting really big with some rrds (in our
> case about 50MB), so processing those files is very time- and
> memory-consuming.

normally you do this once while reorganizing your data files. 
As this is rare operation, and can be batched, I don't care about performance, 
and put flexibility and reliability in favor of it.

> but i dont see the need for this, since you can generate graphs from
> multiple rrds. so, in my opinion, a single rrd for each ds is all you need.
> but i'm not using all features of rrdtool, especially CDEF, so maybe i miss
> the point.

I have a good example, you can search for details in rrfw-devel mailing list arhives.
With few hundred routers, we first kept several RRD files per interface: 
one for in/out bytes, one for in/out packets, and the other two for errors
and discards. 
Joining them all into one RRD file per interface gave a performance boost 
at something like 30%. We talk about thousands of intarfaces, and 
a moderate server platform, without super-large storage memory buffers.

So, if you have dozens of thousands of datasources, saving time on 
searhing a file on the filesystem, opening it, reading RRD header, 
seeking to the position is really important.

And actually the need for rrdmerge tool is when you change some global 
data structure and want to keep the old data. As mentioned, it's a one-time job, 
and performance isn't a factor.

Cheers,
Stan

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