1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
|
Frequently asked questions -- Debian mdadm
==========================================
Also see /usr/share/doc/mdadm/README.recipes.gz
1. How do I change the preferred minor of a RAID array?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See item 12 in /usr/share/doc/mdadm/README.recipes.gz and read the mdadm
manpage (search for 'preferred').
2. How does mdadm determine which /dev/mdX or /dev/md/X to use?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The logic used by mdadm to determine the device node name in the mdadm
--examine output (which is used to generate mdadm.conf) depends on several
factors. Here's how mdadm determines it:
It first checks the superblock version of a given array (or each array in
turn when iterating all of them). Run
mdadm --detail /dev/mdX | sed -ne 's,.*Version : ,,p'
to determine the superblock version of a running array, or
mdadm --examine /dev/sdXY | sed -ne 's,.*Version : ,,p'
to determine the superblock version from a component device of an array.
Version 0 superblocks (00.90.XX)
''''''''''''''''''''''''''''''''
You need to know the preferred minor number stored in the superblock,
so run either of
mdadm --detail /dev/mdX | sed -ne 's,.*Preferred Minor : ,,p'
mdadm --examine /dev/sdXY | sed -ne 's,.*Preferred Minor : ,,p'
Let's call the resulting number MINOR. Also see FAQ 1 further up.
Given MINOR, mdadm will output /dev/md<MINOR> if the device node
/dev/md<MINOR> exists.
Otherwise, it outputs /dev/md/<MINOR>
Version 1 superblocks (01.XX.XX)
''''''''''''''''''''''''''''''''
Version 1 superblocks actually seem to ignore preferred minors and instead
use the value of the name field in the superblock. Unless specified
explicitly during creation (-N|--name) the name is determined from the
device name used, using the following regexp: 's,/dev/md/?(.*),$1,', thus:
/dev/md0 -> 0
/dev/md/0 -> 0
/dev/md_d0 -> _d0
/dev/md/d0 -> d0
/dev/md/name -> name
(/dev/name does not seem to work)
mdadm will append the name to '/dev/md/', so it will always output device
names under the /dev/md/ directory.
If you want to change the name, you can do so during assembly:
mdadm -A -U name -N newname /dev/mdX /dev/sd[abc]X
I know this all sounds inconsistent and upstream has some work to do.
We're on it.
-- martin f. krafft <madduck@debian.org> Wed, 02 Aug 2006 16:38:29 +0100
Revision: $Id$
|
