Let go of the world you knew young padawan. The ZFS handles the mirroring of drives. Do not let spinners stop, the thermodynamics will weaken their spirit and connection to the ZFS.
I am a bit worried about that myself. I've had these 4 drives running 24/7 plugged in to a UPS for about 4 years or so, and so far only 1 has died - replaced it this week.
In order to minimize stress on the hdds and protect that pool from direct access by clients on the LAN, I was considering keeping the same data on the SSD pool. The SSD pool would take snapshots every 1 hour and keep them for only 3 days. Then every 2 days the HDD pool would turn on, run Syncthing (more on this below), mirror changes that occured on the SSD pool and then go back to sleep.
This hdd pool currently takes snapshots every 1 day, keeps them for 2 weeks, then only one every 1 month, then 3 months, 6 months, 1 year. I would change the 1/day to 1/week, 1 per month, etc
I figured a 2 day difference/staggering between the HDD and SSD pools would be enough to detect a Ransonmware attack. Maybe this interval should be longer?
Anyway, back to the point of wear/tear, my reasoning was that by only spinning up once every 2 days and running for a few hours, the trade-off between spin up/down cycling and hours running (as well as power/Temp. saved) would be beneficial.
What do you think?
ps: my CLI-fu isn't enough to master RSync (I've had problems keeping the FreeNAS hdd pool in sync with a local QNAP NAS), so I'll just go for a simpler GUI-based alternative for syncing. I've been reading about this and it's hard to decide between Syncthing, Seafile and Resilio as I have 0 experience with any of them. Since the paid versions aren't too expensive, I wouldn't mind paying if I have to. My list of priorities is data integrity; GUI-based/ease of use; availability in FreeNAS, QNAP, Windows; Low maintenance.
Which would be your preferred solution?