Yeah. Something is strange.
zpool list
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
Mypool 21.8T 17.5T 4.28T - - 10% 80% 1.00x DEGRADED -
media 2.72T 946G 1.79T - - 15% 33% 1.00x ONLINE -
sudo zpool set autoexpand=on Mypool
I have to look into why it is degraded, I suspect that a disk has gone sour.
Might be related to this disk mentioned here: