FreeNAS uses ZFS. There isn't anthing traditional RAID about it.
You can expand it but not by adding a single disk to a parity set (going from five drives to six), only by adding a set of disks (adding another set of five or a similar combination).
You can expand it but not by adding a single disk to a parity set (going from five drives to six), only by adding a set of disks (adding another set of five or a similar combination).