not a question directly related to node-red, but I guess many people here might use influx databases.
So far I had influx data on an external usb stick. Since I now need that port for something else and generally the size of my database is small anyway, I want to store it to the SD card the system is running from (an old cubietruck)
Is it necessary/recommended to play with the wal-fsync-delay or similar settings? Maybe even move the WAL to a ramdisk?
Although am I using a good and large SD card and never had issues so far, I think that it is just not right to write to the file system when ever a sensor reports a new value. Caching those in memory and doing writes every couple hours seems much more sensible.
I do not believe so. I have had 2 Pi's running 24x7x365 for some years now with the same cards and I do nothing to reduce writes to he cards. I have many outputs writing to MQTT with retention and to InfluxDB as well as all of the logging output from the system, Node-RED, InfluxDB, MQTT, Telegraf Unifi controller and more. Admittedly, I do keep my sensors to reporting once a minute generally so I don't go mad with them. But either way, neither card shows any sign of issues even after 3+ years of solid work.
As far as I can tell, 3 factors influence things:
Good, branded SD-Cards.
Large sizes so that wear levelling has plenty of room to work with.
A decent power supply to minimise power issues.
I do have my Pi's attached to a PC UPS which doubtless helps. Though my Pi3 constantly reports low power issues and has occasionally hung or rebooted on me. The Pi2 hasn't skipped a beat in a long time though.