Hardware Raid + hot-replace failed disk

[Pieter Donche]

Suppose you have a system with multiple disks managed by a
hardware RAID controller in a RAID5 of RAID6 configuration,

To FreeBSD it will look like e.g. a single large drive.

If you want to extend your disk space by plugging in an extra
disk, the hardware RAID controller will probably detect it and
add it in his management, but will it be seen by FreeBSD?

How can you make the added disk-space available for FreeBSD.
Can this be done without shutting down the system? How??