Toshiba Magnia Z500 - Manual (Page 19)

Setup
Setup Wizard 16
Hot Spare (Can be used if RAID1 or RAID5 is selected.)
Hot Spare is a spare HDD in stand-by ; when one HDD is
damaged, the hot spare automatically goes on-line.
HDD Assignment
Select the number of HDDs for the RAID configuration from the
list. When "MAX" has been selected, the RAID array is structured
with the maximum number of HDDs ( 4 in the case of MR520, or
2 in the case of on-board IDE RAID controller.).
NOTE: When using the on-board IDE RAID controller,
"RAID5" and "Hot Spare" cannot be selected.