mdadm is a Linux utility used to manage software RAID devices.
The name is derived from the md (multiple device) device nodes it administers or manages, and it replaced a previous utility mdctl. The original name was "Mirror Disk", but was changed as the functionality increased.
It is free software licensed under version 2 or later of the GNU General Public License - maintained and copyrighted to Neil Brown of Suse.
Functionality
Types of physical device
mdadm can handle anything which presents to the kernel as a block device. This can encompass whole disks (/dev/sda), partition...