If you’re having issues with zfsonlinux and your pool not expanding after replacing your hard drives with larger ones then here is a trick to fix it.
# zpool set autoexpand=on {pool name}
# zpool online -e {pool-name} {disk name/id as displayed on zpool status}
Your pool should resize after running the second command. The first command was only to make sure you had set the zfs property that’s needed for the second command to expand the pool.
