Strange resolution in Charts with OH 3.1.0

Old install
Raspi 4 Model B
Java SDK Zulu11.45+27-CA
raspian Rls 10 (Buster)
Openhab Rls 3.0.1-2

New install
Raspi 4 Model B
Java SDK Zulu11.50+19-CA
raspian Rls 10 (Buster)
Openhab Rls 3.1.0

to replace my current OH 3.01 (upgrade from 2.5) installation, I staged a new Openhabian based on latest stable 3.1 release and used the same config files (things, items, sitemap, persistence, …). in PaperUI, configured the same resolution and scaling

but the Charts in OH 3.1 look not as smooth as they do with 3.0.1 or previusly with 2.5. it loos like the vertical steps are far less granular compared to the old 3.0.1 installation.

thought this is the scaling in paper UI but it’s the same in both installation. or maybe OH 3.1 rounds up the received values automatically ?

attached 2 x 2 pictures shows old and new for same item for same timeframe. especially the MQTT topic showing Rasp cpu temp s looks very ugly in 3.1 release.

any help appreciated


Did you perhaps also change your persistence to rrd4j? This issue is one of the reasons why I don’t use rrd4j myself. It stores values on a fixed time scale regardless whether they changed or not, which causes the jaggedness.

nope. i had rrd4j before and after. so everything is the same :frowning:

IMHO rrd4j changed on the move from OH2 to OH3, or more precisely the default datasource setup changed. AFAIK there was now change since then.
The main change is that data-samples are taken now every 10 sec AND that a value for each minute is kept for a week.

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Hi Jürgen,
thanks. good hint. i finally managed to modify the graph configuring datasources in rrd4j.cfg for the affected items. since then, it looks far better.

do you happen to know the default settings used in OH2.5 ? unlike OH3 doc, the old OH2 doc @ rrd4j - Persistence - openHAB 2 - Empowering the Smart Home does not mention the default :frowning:

I would have sworn that the defaults were in the old docs, however…

Read this old post of me: