This option configures the fine details of data layout for RAID5, RAID6,
and RAID10 arrays, and controls the failure modes for
.IR faulty .
+It can also be used for working around a kernel bug with RAID0, but generally
+doesn't need to be used explicitly.
The layout of the RAID5 parity block can be one of
.BR left\-asymmetric ,
"clear" or "none" will remove any pending or periodic failure modes,
and "flush" will clear any persistent faults.
-Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
+The layout options for RAID10 are one of 'n', 'o' or 'f' followed
by a small number. The default is 'n2'. The supported options are:
.I 'n'
number (e.g. it is perfectly legal to have an 'n2' layout for an array
with an odd number of devices).
+A bug introduced in Linux 3.14 means that RAID0 arrays
+.B "with devices of differing sizes"
+started using a different layout. This could lead to
+data corruption. Since Linux 5.4 (and various stable releases that received
+backports), the kernel will not accept such an array unless
+a layout is explictly set. It can be set to
+.RB ' original '
+or
+.RB ' alternate '.
+When creating a new array,
+.I mdadm
+will select
+.RB ' original '
+by default, so the layout does not normally need to be set.
+An array created for either
+.RB ' original '
+or
+.RB ' alternate '
+will not be recognized by an (unpatched) kernel prior to 5.4. To create
+a RAID0 array with devices of differing sizes that can be used on an
+older kernel, you can set the layout to
+.RB ' dangerous '.
+This will use whichever layout the running kernel supports, so the data
+on the array may become corrupt when changing kernel from pre-3.14 to a
+later kernel.
+
When an array is converted between RAID5 and RAID6 an intermediate
RAID6 layout is used in which the second parity block (Q) is always on
the last device. To convert a RAID5 to RAID6 and leave it in this new