This driver lets you combine several hard disk partitions into one
logical block device. This can be used to simply append one
partition to another one or to combine several redundant hard disks
into a RAID1/4/5 device so as to provide protection against hard
disk failures. This is called "Software RAID" since the combining of
the partitions is done by the kernel. "Hardware RAID" means that the
combining is done by a dedicated controller; if you have such a
controller, you do not need to say Y here.

More information about Software RAID on Linux is contained in the
Software RAID mini-HOWTO, available from
<https://www.tldp.org/docs.html#howto>. There you will also learn
where to get the supporting user space utilities raidtools.

If unsure, say N.

source code:

drivers/md/