Marvell RAID Utility Help
You must use a physical disk that is unconfigured. A physical disk that is fully or even partially configured cannot be set as a spare physical disk. Spare physical disk are needed for Auto-Rebuild functions.
To set a spare drive
Start the MRU
Mouse over the Physical Devices tab and click the Physical Disks tab.
Select a physical disk as the target spare drive, and then click Set Spare.
The Set Spare button changes to Clear Spare. If you click View All, your physical disk icon would have the letters 'SP' beside it.