I'll point you this this as it may be of some interest:
The crux of the matter is use which ever database is the best for what you want to do with the data.
I use a blanket "store everything" into MapDB for restoreOnStartup. I don't see the need for saving more than the most recent value for the bulk of my Items but I do like the default option to be to restore everything to its previous state and then I have rules which update sensor values or recalculate state where needed.
I used to use rrd4j for keeping historic data because it is fixed size and therefore will never need maintenance. However, I've since refactored all of those cases out so no longer use rrd4j at all.
For charting I use InfluxDB and Grafana (dockerized). If find they do not consume many resources at all and the few Items I have which get charted or for which I track historic data is small so I'm not worried about having to do maintenance on the DB if it grows too large for many many years.
I'm in the middle of a ground up rebuild of my entire home automation system (for the regulars, this is why I've been so absent lately) so I may change my mind as I go.
But if you are running on anything larger than a board computer performance should not be an issue for you. For comparison, I'm running the following on an old Asus Bamboo laptop with an i7 Intel CPU but only 4 GB RAM, running Ubuntu 16
- samba shares: docker
- gogs: docker
- plexmediaserver: docker
- mosquitto: docker
- influxdb: docker
- grafana: docker
- openhab: docker
- zoneminder: docker (not yet reinstalled)
- crashplan: (not yet reinstalled)
- OPNsense: VirtualBox (not yet reinstalled, probably wont)
The only time I ever saw performance problems was when I tried to watch something streamed from Plex that required transcoding (e.g. from one of the channels) at the same time CrashPlan was receiving a backup from one of my other machines.
And in relation to the rebuild: always make backups and make them frequently! Though this is giving me the opportunity to automate the build and config of my main server (I'm really quite enjoying Ansible) and I'm finding as I rewrite my rules I'm being more consistent and concise.
Once I get back to where I was functionally I may post some or all of them as an examples.