See ZFS.
Convert a single-disk stripe on a zpool to a mirror stripe
Drives
Jails
NIC not recognized
Plex
Plugins
Pool
Replace a Drive
Replace Boot Drive
re0 Watchdog Timeout
Update FreeNAS
https://www.ixsystems.com/documentation/freenas/
https://www.ixsystems.com/community/
https://www.reddit.com/r/freenas/