Other useful things about ZFS:

- get to know the difference between zpool-attach(8) and zpool-replace(8).

- this one will tell you where your space is used:

    # zfs list -t all -o space
    NAME                      AVAIL   USED  USEDSNAP  USEDDS  USEDREFRESERV  USEDCHILD
    (...)

- ZFS Boot Environments is the best feature to protect your OS before major changes/upgrades

--- this may be useful for a start: https://is.gd/BECTL

- this command will tell you all history about ZFS pool config and its changes:

    # zpool history poolname
    History for 'poolname':
    2023-06-20.14:03:08 zpool create poolname ada0p1
    2023-06-20.14:03:08 zpool set autotrim=on poolname
    2023-06-20.14:03:08 zfs set atime=off poolname
    2023-06-20.14:03:08 zfs set compression=zstd poolname
    2023-06-20.14:03:08 zfs set recordsize=1m poolname
    (...)

- the guide misses one important info:

  --- you can create 3-way mirror - requires 3 disks and 2 may fail - still no data lost

  --- you can create 4-way mirror - requires 4 disks and 3 may fail - still no data lost

  --- you can create N-way mirror - requires N disks and N-1 may fail - still no data lost

  (useful when data is most important and you do not have that many slots/disks)