It seems to me that domoticz is plotting graphs using some kind of smoothing (maybe exponential smoothing).

sure, Raspi is worth a try.

The hardware is: TP-Link C7 V5 wifi router. You are right for the resources usage. I have the following services running: nginx (to host my web page), ddns (to make my router reachable from the internet with a fixed hostname), dhcp server, openvpn server, and domoticz. Untill now, there is no issue ...

The reasons:
1) I don't have a raspi where I can install domoticz.
2) I already have the wifi router at home with openWRT and running few services.

I finally solved this issue as follows: 1- I created a RAM disk as /var/log 2- I created the following links in /tmp/lib/domoticz/ : domoticz.db-wal -> /tmp/log/domoticz.db-wal domoticz.db-shm -> /tmp/log/domoticz.db-shm By doing this, my statistics data are no lost after the router restart. 3 ...

Hello,
I am a newbie. I installed domoticz on openWRT (in a TP-Link C7 V5 wifi router) using the command : opkg install domoticz. Any inserted setup (using the GUI) gets deleted after router restart. Where shall I dig? Thank you very much.
Regards
Zak