by lundman » Thu Jun 20, 2019 3:31 pm
Auto-expand doesn't kick in when you remove a smaller device - and in your case autoexpand was off anyway. You can
actually tell it to expand manually, using "zpool online -e pool device" which should have worked with your 1 4TB disk.
But with autoexpand on, and replacing the final device in your mirror, ZFS kicked in an expanded it for you.
BTW, the zpool.cache only stores the (names of) pools that it should import on boot. Nothing else, so no real
reason to remove it. In addition to that, I recently noticed the OSX autoimport script run by launchctl completely
ignores zpool.cache, and just runs "zpool import -a". But perhaps one day we will fix that up.