Intel chipset (BIOS) RAID migration
Users of Intel-based systems with Intel chipsets may encounter some systems where RAID is enabled, but users wish to add additional harddisks or migrate RAID types.
Standard Dell and HP business-class desktops such as the Optiplex 755 and 8100 Elite all support Intel chipset RAID in some or most configurations— a common setup is a two-disk RAID1 to protect from a single disk hardware failure.
A common question is whether or not the RAID1 can be migrated (most users mean expanded) to a 3-disk or more RAID5 or a 4-disk RAID10.
The answer to the former is: no. The answer to the latter also is: no.
The following link from Intel describes the migration types supported without having to destroy/recreate all data on the RAID:
The link above discusses the Intel ICH7R, ICH9R, ICH10R, the current PCH-series, and most variants in-between.