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1Subject: ANNOUNCE: mdadm 3.0-devel1 - A tool for managing Soft RAID under Linux
2
3I am pleased to announce the availability of
4 mdadm version 3.0-devel1
5
6It is available at the usual places:
7 countrycode=xx.
8 http://www.${countrycode}kernel.org/pub/linux/utils/raid/mdadm/
9and via git at
10 git://neil.brown.name/mdadm
11 http://neil.brown.name/git?p=mdadm
12
13Note that this is a "devel" release. It is not intended for
14production use yet, but rather for testing and ongoing development.
15
16The significant change which justifies the new major version number is
17that mdadm can now handle metadata updates entirely in userspace.
18This allows mdadm to support metadata formats that the kernel knows
19nothing about.
20
21Currently two such metadata formats are supported:
22 - DDF - The SNIA standard format
23 - Intel Matrix - The metadata used by recent Intel ICH controlers.
24
25The manual pages have not yet been updated, but here is a brief outline.
26
27Externally managed metadata introduces the concept of a 'container'.
28A container is a collection of (normally) physical devices which have
29a common set of metadata. A container is assembled as an md array, but
30is left 'inactive'.
31
32A container can contain one or more data arrays. These are composed from
33slices (partitions?) of various devices in the container.
34
35For example, a 5 devices DDF set can container a RAID1 using the first
36half of two devices, a RAID0 using the first half of the remain 3 devices,
37and a RAID5 over thte second half of all 5 devices.
38
39A container can be created with
40
41 mdadm --create /dev/md0 -e ddf -n5 /dev/sd[abcde]
42
43or "-e imsm" to use the Intel Matrix Storage Manager.
44
45An array can be created within a container either by giving the
46container name and the only member:
47
48 mdadm -C /dev/md1 --level raid1 -n 2 /dev/md0
49
50or by listing the component devices
51
52 mdadm -C /dev/md2 --level raid0 -n 3 /dev/sd[cde]
53
54The assemble a container, it is easiest just to pass each device in turn to
55mdadm -I
56
57 for i in /dev/sd[abcde]
58 do mdadm -I $i
59 done
60
61This will assemble the container and the components.
62
63Alternately the container can be assembled explicitly
64
65 mdadm -A /dev/md0 /dev/sd[abcde]
66
67Then the components can all be assembled with
68
69 mdadm -I /dev/md0
70
71For each container, mdadm will start a program called "mdmon" which will
72monitor the array and effect any metadata updates needed. The array is
73initially assembled readonly. It is up to "mdmon" to mark the metadata
74as 'dirty' and which the array to 'read-write'.
75
76The version 0.90 and 1.x metadata formats supported by previous
77versions for mdadm are still supported and the kernel still performs
78the same updates it use to. The new 'mdmon' approach is only used for
79newly introduced metadata types.
80
81Any testing and feedback will be greatly appreciated.
82
83NeilBrown 18th September 2008
84