FreeNAS 11.2 growing/expanding/adding more storage space by replacing array disks with larger ones

You can not add additional disks to an existing array (AKA: 4-disk RAID6/z2 to a 5-disk RAID6/z2) but you can very very easily replace disks in the array with larger disks and the available pool size will increase automatically. (!! ... subject to limitations of your smallest disk(s))

FreeNAS 11.2 from scratch, part 1: make your USB booter
FreeNAS 11.2 from scratch, part 1: ma...

FreeNAS 11.2 from scratch, part 2: create a user & pool of disks, configure & share its dataset
FreeNAS 11.2 from scratch, part 2: cr...

creating FreeNAS boot-USB with VirtualBox
creating FreeNAS boot-USB with Virtua...

Installing FreeNAS to (virtual) boot-disk in VirtualBox (for tryout/testing purposes)
Installing FreeNAS to (virtual) boot-...

adding virtual disks to FreeNAS VM in VirtualBox
adding virtual disks to FreeNAS VM in...

starting FreeNAS in VirtualBox and port forwarding so it's accessible
starting FreeNAS in VirtualBox and po...

FreeNAS 11.2 first visit via Firefox on localhost and adding first admin user
FreeNAS 11.2 first visit via Firefox ...

FreeNAS 11.2 creating RAID-style pool of disks and setting ownership of its default dataset
FreeNAS 11.2 creating RAID-style pool...

FreeNAS 11.2 install Plex server plugin with mountpoint outside its Jail (and group ownership trick)
FreeNAS 11.2 install Plex server plug...