[Solved] RRD4J does not display Data over the time

You seem to have a syntax problem in your rrd4j.persist. We both might miss the difference by just looking at it. This is mine:

/ *RRD4J CONFIG*
//

Strategies {
    everyMinute : "0 * * * * ?"
    everyHour : "0 0 * * * ?"
    everyDay : "0 0 0 * * ?"
}
Items { temp_20  :strategy=everyMinute
}

We are not seeing any message that a value is persisted, try it with a new rrd4j.persist file, if the startup errors are gone we could move a step forward.

Regarding the other error, that rings a bell but I have to dig a bit deeper in my memory, although the “___HK2_Generated…” was not related to persistence (I think).
What version of openHAB do you use and what hardware. It could be related with a problem when updating from 2.3 to 2.4 and the caused changes of bindings installed.
[Edit]
I found a relating thread started by me:

The size of the log files is always growing, if they are to big, the old one is saved and a new one gets started. They are not deleted when openHAB is restarted.