rrdtool fetch gives "not an RRD file"

[Patrik Åkerfeldt]

I've created a number of rrd databases from the rrd4j persistence bundle. But when I try to read from them using rrdtool I get:

$ sudo rrdtool fetch Temperature_Bathroom.rrd LAST

ERROR: 'Temperature_Bathroom.rrd' is not an RRD file

Why could that be?

Thanks,

på

[Patrik Åkerfeldt]

Oh, maybe they're not even meant to work together?

/på

[Cyril Jaquier]

Hi,
 

Note that Rrd4j uses binary format different from RRDTool's format. You cannot use this class to manipulate RRD files created with RRDTool. However, if you perform the same sequence of create, update and fetch operations, you will get exactly the same results from Rrd4j and RRDTool.

 

from http://rrd4j.googlecode.com/svn/trunk/javadoc/reference/org/rrd4j/core/RrdDb.html

Regards,
Cyril

[frou...@gmail.com]

So the answer is that we cannot retrieve the raw data from rrd?

So must we also persist the same data in db4o?

Isn't it duplication?

FDR

[Chris Jackson]

It depends on what you want to do. You shouldn't need to use rrdtool to extract data from the persistence stores in openHAB for routine tasks. openHAB provides methods to retrieve this data itself through the sitemap charts, rule methods etc - although if you want to do something more advanced, then you'd need to use a tool that is compatible with the rrd4j format (if such a thing exists - I don't know too much about it as I'm using mySQL).

Alternatively you could possibly use the REST interface that is exposed through the HABmin bundle.

Chris

[Franck Rougier]

That sounds good and your response is reassuring.
I have a bunch of temperature sensors and I needed to get all the data for further analysis. Unfortunately I was only persisting to rrd thinking that rrdtools could dump to XML.
But it turns out that rrdtools only works with rrdj. So now I found myself storing data in the default persistence engine to get to the data.
I think I will explore MySQL persistence and link rrd to generate graphics.
Use of the REST methods would puts pressure on my server to retrieve the data.

Thank you.



Franck Rougier
917-400-0189