.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\" See file COPYING in distribution for details.
-.TH MDADM 8 "" v3.0.2
+.TH MDADM 8 "" v3.1.1
.SH NAME
mdadm \- manage MD devices
.I aka
.TP
.BR \-e ", " \-\-metadata=
Declare the style of RAID metadata (superblock) to be used. The
-default is 0.90 for
+default is 1.1 for
.BR \-\-create ,
and to guess for other operations.
The default can be overridden by setting the
Options are:
.RS
-.IP "0, 0.90, default"
+.IP "0, 0.90"
Use the original 0.90 format superblock. This format limits arrays to
28 component devices and limits component devices of levels 1 and
greater to 2 terabytes.
-.IP "1, 1.0, 1.1, 1.2"
+.IP "1, 1.0, 1.1, 1.2 default"
Use the new version-1 format superblock. This has few restrictions.
The different sub-versions store the superblock at different locations
on the device, either at the end (for 1.0), at the start (for 1.1) or
-4K from the start (for 1.2).
+4K from the start (for 1.2). '1' is equivalent to '1.0', 'default' is
+equivalent to '1.1'.
.IP ddf
Use the "Industry Standard" DDF (Disk Data Format) format defined by
SNIA.
.TP
.BR \-c ", " \-\-chunk=
-Specify chunk size of kibibytes. The default is 64.
+Specify chunk size of kibibytes. The default when creating an
+array is 512KB. To ensure compatibility with earlier versions, the
+default when Building and array with no persistent metadata is 64KB.
This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
.TP
This is a synonym for
.B \-\-chunk
but highlights the different meaning for Linear as compared to other
-RAID levels.
+RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in
+use, and is 0K (i.e. no rounding) in later kernels.
.TP
.BR \-l ", " \-\-level=
size that is at-least 4 and requires no more than 2^21 chunks.
When using an
.B internal
-bitmap, the chunksize is automatically determined to make best use of
-available space.
+bitmap, the chunksize defaults to 64Meg, or larger if necessary to
+fit the bitmap into the available space.
.TP
.BR \-W ", " \-\-write\-mostly
to determine the maximum usable amount of space on each device and
update the relevant field in the metadata.
-.ig XX
+.ig
.TP
.B \-\-auto\-update\-homehost
This flag is only meaningful with auto-assembly (see discussion below).
.I mdadm
will rescan for any arrays at all and will assemble them and update the
homehost to match the current host.
-.XX
+..
.SH For Manage mode:
.B /dev/md/
(the name will have any 'host' prefix stripped first).
-.ig XX
+.ig
If
.I mdadm
cannot find any array for the given host at all, and if
The reason for requiring arrays to be tagged with the homehost for
auto assembly is to guard against problems that can arise when moving
devices from one host to another.
-.XX
+..
.SH BUILD MODE
.I md
metadata is found, the device is rejected.
-.ig XX
+.ig
.IP +
Does the metadata match an expected array?
The metadata can match in two ways. Either there is an array listed
.I mdadm
is not able to positively identify the array as belonging to the
current host, the device will be rejected.
-.XX
+..
.I mdadm
keeps a list of arrays that it has partially assembled in