radmon.org down 19/04/20

Rpi always do strange things with drives.
At the moment I use 2 of these
https://www.amazon.com/dp/B01LZ0LCTU/ref=pe_825000_114212990_TE_FOCE_n_id with 128Gb Msata.
It works great and fast.

An alternative to the R-Pi is a mini-ITX board with a Celeron J-series CPU. I'm using one that maxes out at 10w hypothetically but I've not seen it go above 4w. Most of the time when it is not sleeping it's a watt or two measured with a K-a-W. Another benefit is no fan is needed. The trick is to get one that has a 12v power jack & for even greater power savings, can utilize a M.2/mSATA/DOM-SATA drive. With no fan & any SSD (even a regular SATA one) it's completely silent & very efficient. It also works to use one with a standard ATX PSU connector and a picoPSU. With either set up much of the efficiency depends on how you provide 12v; some adapter bricks are amazingly inefficient.

This would also fit into your plan to run everything off solar + batteries especially if the entire power set-up is 12v from solar panels to batteries to mobo power-in. The less conversion the better, etc..