Docs: RRD conversion (format is dependent on platform)

[holgerfriedrich]

This issue is related to OH5 preparations. A lot of users will need to migrate their setup to 64-bit.

RRD database format is dependent on the platform, i.e. during migration from 32-bit to 64-bit system those databases need special treatment.
It seems that an xml export / import is necassary.

See for example https://blog.remibergsma.com/2012/04/30/rrdtool-moving-data-between-32bit-and-64bit-architectures/

As this is the default database format, we need to support users during migration. This is about documentation of the necessary steps. In addition, we should implement some tooling in the openHABian tool.

[rkoshak]

Is this something that upgradeTool could do?

[holgerfriedrich]

There is actually no need to convert data. We are using RRD4J database format, which is not dependent on platform.
This is also mentioned as one of the main selling points of RRD4J:
https://github.com/rrd4j/rrd4j#why-rrd4j

Why RRD4J?
Portable files, RRDTool files are not

I just imported data from my old backups and could still visualize it on my 64-bit system.

Sorry for the confusion.