- Flashed Armbian_20.08.8_Helios64_buster_legacy_4.4.213.img.xz and went through initial setup.
- sudo apt-get update && sudo apt-get dist-upgrade -y
- sudo apt-get install linux-headers-legacy-rk3399
- sudo apt-get install zfs-dkms -t buster-backports
- installed OMV through armbian-config
- logged in to OMV web interface and enabled the omv-extras repo
- still in OMV, went to Plugins and installed openmediavault-zfs (regular, not armhf)
- enabled SMART monitoring for all disks (not sure if relevant)
- From the newly-added "ZFS" section in OMV, imported my ZFS pool (4x4TB RAID-Z2).
- Created some shared folders and shared them via NFS and Samba
- Started a scrub on the ZFS pool, this puts some medium/high load on the CPU and disks.
- Have two clients (Proxmox) accesssing a couple of VM disks via NFS.

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if someone wants to shutdown their unit on powerloss:

create file: /etc/udev/rules.d/15-gpio-charger.rules
SUBSYSTEM=="power_supply", ENV{POWER_SUPPLY_ONLINE}=="0", RUN+="/usr/sbin/halt"

i'd love to know a way to start that unit when power is available again though.
on 4.4 the system crashes on halt. but as it does this after all services are stopped and the disks are synced this is not really a problem.
on 5.8 the system stops and "system halted" appears on serial console - BUT it is still on and fans are spinning.
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Is it possible set the fan speed of the pwm fans somehow? For me the fan connected to P6 never ever starts, whereas the fan connected to P7 always runs at full speed (well, a little slower when on battery power).
You can do that through /etc/fancontrol but the syntax is a litte strange. 
I tweaked mine to start the fans earlier (i have replaced the original ones with two 80mm noctua which are more silent) 
cat /sys/class/hwmon/hwmon0/pwm1                              104
cat /sys/class/hwmon/hwmon1/pwm1                              89
Shows current fan speed. Values are between 0 and 255
FCTEMPS connect cpu temp to both fans. 
My /etc/fancontrol
INTERVAL=10
FCTEMPS=/dev/fan-p6/pwm1=/dev/thermal-cpu/temp1_input /dev/fan-p7/pwm1=/dev/thermal-cpu/temp1_input
MINTEMP=/dev/fan-p6/pwm1=45 /dev/fan-p7/pwm1=45
MAXTEMP=/dev/fan-p6/pwm1=70 /dev/fan-p7/pwm1=70
MINSTART=/dev/fan-p6/pwm1=60 /dev/fan-p7/pwm1=60
MINSTOP=/dev/fan-p6/pwm1=29 /dev/fan-p7/pwm1=29
MINPWM=20

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