FT (fault tolerant) volume
Refers to a RAID volume that was originally created in Windows NT Disk Administrator. These volumes include spanned volumes (volume sets), mirrored volumes (mirror sets), striped volumes (stripe sets), and RAID-5 volumes (stripe sets with parity). The FT refers to fault tolerant, even though some of the volume sets are not fault tolerant.
Windows Server 2003 does not support FT volumes. On systems that are running Windows 2000, Storage Foundation for Windows can maintain and repair these volumes, but it cannot recreate them. However, a disk that contains these volumes can be upgraded to dynamic, and the volumes will be converted to dynamic volumes of the corresponding type.