The SNIA common RAID disk data format (DDF) defines a standard data structure describing how data is formatted across disks in a RAID group. The DDF structure allows a basic level of interoperability between different suppliers of RAID technology. The common RAID DDF structure benefits storage users by enabling in-place data migration or recovery after controller failure using systems from different vendors.[1]
DDF is an external metadata format that is compatible with the mdraid subsystem in the Linux kernel. The mdadm command-line utility is a part of the mdraid subsystem.[2]