17.3. Linux RAID Subsystems
RAID in Linux is composed of the following subsystems:
Linux Hardware RAID controller drivers
Hardware RAID controllers have no specific RAID subsystem in Linux. Because they use special RAID chipsets, hardware RAID controllers come with their own drivers; these drivers allow the system to detect the RAID sets as regular disks.
mdraidsubsystem was designed as a software RAID solution for Linux; it is also the preferred solution for software RAID under Linux. This subsystem uses its own metadata format, generally referred to as native
mdraidalso supports other metadata formats, known as external metadata. Red Hat Enterprise Linux 6 uses
mdraidwith external metadata to access ISW / IMSM (Intel firmware RAID) sets.
mdraidsets are configured and controlled through the
Device-mapper RAID or
dmraidrefers to device-mapper kernel code that offers the mechanism to piece disks together into a RAID set. This same kernel code does not provide any RAID configuration mechanism.
dmraidis configured entirely in user-space, making it easy to support various on-disk metadata formats. As such,
dmraidis used on a wide variety of firmware RAID implementations.
dmraidalso supports Intel firmware RAID, although Red Hat Enterprise Linux 6 uses
mdraidto access Intel firmware RAID sets.