--- /dev/null
+Subject: ANNOUNCE: mdadm 3.0-rc1 - A tool for managing Soft RAID under Linux
+
+I am pleased to announce the availability of
+ mdadm version 3.0-rc1
+
+It is available at the usual places:
+ countrycode=xx.
+ http://www.${countrycode}kernel.org/pub/linux/utils/raid/mdadm/
+and via git at
+ git://neil.brown.name/mdadm
+ http://neil.brown.name/git?p=mdadm
+
+This is a "release candidate" which means that I think it is safe
+to use and that there will be no significant change in functionality
+before release.
+
+The man pages aren't really "release candidate" yet but I will be
+working on them before the final release.
+
+The most significant changes since -devel3 relate to the names of md
+devices as they appear in /dev and /dev/md/, and in particular the names
+that are used when an array is assembled with "--incremental" or with
+"mdadm --assemble --scan" when there are no ARRAY lines in mdadm.conf.
+In these cases mdadm needs to deduce a name to use, and to try to
+avoid using a name that a different array might have a stronger claim to.
+The rules are:
+ - if the array is mentioned in mdadm.conf, use the name given there.
+ - if the array appear to have been created for "this host" using the
+ "homehost" concept, trust the name given in the metadata
+ - if the new setting "HOMEHOST <ignore>" is given (can be in mdadm.conf
+ or on command line) the the name given in the metadata is not
+ associated with some other array by mdadm.conf, then trust the
+ name given in the metadata
+ - otherwise use the name in the metadata, but in an untrusted manner.
+
+If a name is untrusted, or if the name is already in use by another
+array, then a numeric suffix like "_0", "_1" is appended to create
+a unique name for the array.
+
+That name is then used to create a device file in /dev/md/.
+
+So if all arrays needed for boot will always be listed in
+/etc/mdadm.conf, then it is appropriate to add "HOMEHOST <ignore>" to
+mdadm.conf and there is no risk of conflicting names. However if you
+want auto-assemble to assemble all arrays at boot time and you don't
+want to list them in mdadm.conf, then don't give "HOMEHOST <ignore>"
+either else there could be a risk of the wrong array being assembled
+for a given name.
+
+
+
+The following is the same introduction to 3.x as appeared in
+previous announcements.
+
+Any testing and feedback will be greatly appreciated.
+
+NeilBrown 11th May 2009
+
+
+=====================================================
+
+The significant change which justifies the new major version number is
+that mdadm can now handle metadata updates entirely in userspace.
+This allows mdadm to support metadata formats that the kernel knows
+nothing about.
+
+Currently two such metadata formats are supported:
+ - DDF - The SNIA standard format
+ - Intel Matrix - The metadata used by recent Intel ICH controlers.
+
+Also the approach to device names has changed significantly.
+
+If udev is installed on the system, mdadm will not create any devices
+in /dev. Rather it allows udev to manage those devices. For this to work
+as expected, the included udev rules file should be installed.
+
+If udev is not install, mdadm will still create devices and symlinks
+as required, and will also remove them when the array is stopped.
+
+mdadm now requires all devices which do not have a standard name (mdX
+or md_dX) to live in the directory /dev/md/. Names in this directory
+will always be created as symlinks back to the standard name in /dev.
+
+The man pages contain some information about the new externally managed
+metadata. However see below for a more condensed overview.
+
+Externally managed metadata introduces the concept of a 'container'.
+A container is a collection of (normally) physical devices which have
+a common set of metadata. A container is assembled as an md array, but
+is left 'inactive'.
+
+A container can contain one or more data arrays. These are composed from
+slices (partitions?) of various devices in the container.
+
+For example, a 5 devices DDF set can container a RAID1 using the first
+half of two devices, a RAID0 using the first half of the remain 3 devices,
+and a RAID5 over thte second half of all 5 devices.
+
+A container can be created with
+
+ mdadm --create /dev/md0 -e ddf -n5 /dev/sd[abcde]
+
+or "-e imsm" to use the Intel Matrix Storage Manager.
+
+An array can be created within a container either by giving the
+container name and the only member:
+
+ mdadm -C /dev/md1 --level raid1 -n 2 /dev/md0
+
+or by listing the component devices
+
+ mdadm -C /dev/md2 --level raid0 -n 3 /dev/sd[cde]
+
+To assemble a container, it is easiest just to pass each device in turn to
+mdadm -I
+
+ for i in /dev/sd[abcde]
+ do mdadm -I $i
+ done
+
+This will assemble the container and the components.
+
+Alternately the container can be assembled explicitly
+
+ mdadm -A /dev/md0 /dev/sd[abcde]
+
+Then the components can all be assembled with
+
+ mdadm -I /dev/md0
+
+For each container, mdadm will start a program called "mdmon" which will
+monitor the array and effect any metadata updates needed. The array is
+initially assembled readonly. It is up to "mdmon" to mark the metadata
+as 'dirty' and which the array to 'read-write'.
+
+The version 0.90 and 1.x metadata formats supported by previous
+versions for mdadm are still supported and the kernel still performs
+the same updates it use to. The new 'mdmon' approach is only used for
+newly introduced metadata types.
projects / thirdparty / mdadm.git / commitdiff
