root@r710nr2:~# zpool status
pool: rpool
state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
the pool may no longer be accessible by software that does not support
the features. See zpool-features(5) for details.
scan: scrub repaired 0B in 21h18m with 0 errors on Sun Dec 9 21:42:54 2018
config:
NAME STATE READ WRITE CKSUM
rpool ONLINE 0 0 0
raidz1-0 ONLINE 0 0 0
sdb2 ONLINE 0 0 0
sdc2 ONLINE 0 0 0
sdd2 ONLINE 0 0 0
sde2 ONLINE 0 0 0
sdf2 ONLINE 0 0 0
sda1 ONLINE 0 0 0
errors: No known data errors
root@r710nr2:~# zpool remove rpool sda1
cannot remove sda1: only inactive hot spares, cache, or log devices can be removed