EduardCH

Thanks for reply. I was talking about raid5 or raidz1. The idea is to have only one drive for parity.
 
I already figured it out. I do have experience in ZFS on x86. But I decided for myself that I can not use ZFS (or btrfs) on ARM and feel safe for data at the same time. Will wait and see. I'm sure that this will change soon.
 
This is exactly where I came to. I've set up SnapRaid and mergerfs. For home usage it's almost perfect.
 
You right, especially when there are not so much options, since ZFS and Btrfs are not ready yet. But I hope since we now have good ARM based hardware storage solution, like Helios64, this will change soon.

If anyone is interested, I've created a shell script that can be run with cron to check A/C and battery status, and do a graceful shutdown when a battery threshold is met.  It also logs power outages, battery drain when off A/C, and when it posts a shutdown (if any).  This is a simple script, nothing fancy, but works for me.  It has a granularity of one minute (cron is limited to one minute intervals), but I've been able to keep the system up on heavy load for 4-5 minutes before the script generates a shutdown on low battery.
 
The script is generous -- it waits for 916mV or less before a shut-down.  This value was provided by the KOBOL team on their Wiki as the recommended shutdown threshold for the battery, but can be changed via the script.  You can comment out any file-logging lines, or change the file location, also from within the script.  I've heavily commented it, should be pretty easy to follow.
 
Copy the script below into a file named whatever you choose, place it where you want to run it, and cron it to get it going.  It should only create disk writes when the power is out or when shutting down from battery drain on no A/C (a few lines once per minute), and will create no disk writes  if you comment out the logging.
 
 
Let me know how it works for you, if you use it.  I've been testing it for the past couple of days, and it's worked as intended.  I'm always open to code tips, and I'm still learning, so any advice is appreciated.