$1/day? At 100W average power usage, that’s 2.4kWh per day, suggesting that where you live, the price is 41.67 cents per kWh, roughly double that of California.
Is electricity that expensive where you live?
Edit: it’s been a while since I lived in the Bay area, I hadn’t realized that the electricity price now ranges from 38-62 cents per kWh, depending on rate plan and time.
BTRFS is stable for all RAID levels except for RAID 5 and 6 (because of the write hole). I’m using it with RAID 10.