1 Tools that manage md devices can be found at
2 http://www.<country>.kernel.org/pub/linux/utils/raid/....
6 You can boot with your md device with the following kernel command
9 for old raid arrays without persistent superblocks:
10 md=<md device no.>,<raid level>,<chunk size factor>,<fault level>,dev0,dev1,...,devn
12 for raid arrays with persistent superblocks
13 md=<md device no.>,dev0,dev1,...,devn
15 md device no. = the number of the md device ...
22 raid level = -1 linear mode
24 other modes are only supported with persistent super blocks
26 chunk size factor = (raid-0 and raid-1 only)
27 Set the chunk size as 4k << n.
29 fault level = totally ignored
31 dev0-devn: e.g. /dev/hda1,/dev/hdc1,/dev/sda1,/dev/sdb1
33 A possible loadlin line (Harald Hoyer <HarryH@Royal.Net>) looks like this:
35 e:\loadlin\loadlin e:\zimage root=/dev/md0 md=0,0,4,0,/dev/hdb2,/dev/hdc3 ro
37 -------------------------------
38 The md driver can support a variety of different superblock formats.
39 (It doesn't yet, but it can)
41 The kernel does *NOT* autodetect which format superblock is being
42 used. It must be told.
44 Superblock format '0' is treated differently to others for legacy
48 General Rules - apply for all superblock formats
49 ------------------------------------------------
51 An array is 'created' by writing appropriate superblocks to all
53 It is 'assembled' by associating each of these devices with an
54 particular md virtual device. Once it is completely assembled, it can
57 An array should be created by a user-space tool. This will write
58 superblocks to all devices. It will usually mark the array as
59 'unclean', or with some devices missing so that the kernel md driver
60 can create approrpriate redundancy (copying in raid1, parity
61 calculation in raid4/5).
63 When an array is assembled, it is first initialised with the
64 SET_ARRAY_INFO ioctl. This contains, in particular, a major and minor
65 version number. The major version number selects which superblock
66 format is to be used. The minor number might be used to tune handling
67 of the format, such as suggesting where on each device to look for the
70 Then each device is added using the ADD_NEW_DISK ioctl. This
71 provides, in particular, a major and minor number identifying the
74 The array is started with the RUN_ARRAY ioctl.
76 Once started, new devices can be added. They should have an
77 appropriate superblock written to them, and then passed be in with
80 Devices that have failed or are not yet active can be detached from an
81 array using HOT_REMOVE_DISK.
84 Specific Rules that apply to format-0 super block arrays, and
85 arrays with no superblock (non-presistant).
86 -------------------------------------------------------------
88 An array can be 'created' by describing the array (level, chunksize
89 etc) in a SET_ARRAY_INFO ioctl. This must has major_version==0 and
91 Then uninitialised devices can be added with ADD_NEW_DISK. The
92 structure passed to ADD_NEW_DISK must specify the state of the device
93 and it's role in the array.
95 One started with RUN_ARRAY, uninitialised spares can be added with