# Auto mount 唔成功

SystemRescueCD 's dmesg

[   31.898508] md: Autodetecting RAID arrays.
[   31.898943] md: invalid raid superblock magic on sdb1
[   31.898947] md: sdb1 does not have a valid v0.90 superblock, not importing!
...

# Exam foreign endian arrary members

mdadm -E /dev/sdb1 /dev/sdc1 /dev/sdd1

mdadm: No md superblock detected on /dev/sdb1.

# -e, --metadata=

# Declare the style of RAID metadata (superblock) to be used.(Default: 1.2)

mdadm -E -e0.9 /dev/sdb1

/dev/sdb1:
          Magic : a92b4efc
        Version : 0.90.00
           UUID : de1014dd:82c5e2df:3017a5a8:c86610be
  Creation Time : Wed Apr  6 07:36:44 2016
     Raid Level : raid1
  Used Dev Size : 2490176 (2.37 GiB 2.55 GB)
     Array Size : 2490176 (2.37 GiB 2.55 GB)
   Raid Devices : 12
  Total Devices : 3
Preferred Minor : 0

    Update Time : Fri Feb 22 07:43:48 2019
          State : clean
 Active Devices : 3
Working Devices : 3
 Failed Devices : 9
  Spare Devices : 0
       Checksum : b6ce7c96 - correct
         Events : 5934269


      Number   Major   Minor   RaidDevice State
this     0       8       17        0      active sync   /dev/sdb1

   0     0       8       17        0      active sync   /dev/sdb1
   1     1       8       33        1      active sync   /dev/sdc1
   2     2       8       49        2      active sync   /dev/sdd1
   3     3       0        0        3      faulty removed
   4     4       0        0        4      faulty removed
   5     5       0        0        5      faulty removed
   6     6       0        0        6      faulty removed
   7     7       0        0        7      faulty removed
   8     8       0        0        8      faulty removed
   9     9       0        0        9      faulty removed
  10    10       0        0       10      faulty removed
  11    11       0        0       11      faulty removed

# mount it

mdadm -AU byteorder /dev/md0 /dev/sdb1 /dev/sdc1  /dev/sdd1

mdadm --assemble --update=byteorder /dev/md0 /dev/sdb1 /dev/sdc1  /dev/sdd1

-U, --update=

Update the superblock on each device while assembling the array.

Argument: uuid,  name, homehost, resync, byteorder ...

uuid

will change the uuid of the array

--uuid UUID, If no --uuid is given, a random UUID is chosen

name

change the name of the array as  stored  in the  superblock

homehost

will change the homehost as recorded in  the superblock.

resync

will cause the array to be marked dirty meaning that any redundancy in the array  

(e.g.  parity  for  RAID5, copies  for  RAID1)

byteorder

allows arrays to be moved between machines with different byte-order

correct that order before assembling the array (first time after a move)

This is only valid with original (Version 0.90) superblocks.

--update=byteorder => byteorder reversed

summaries

will correct the summaries in the superblock.  

That is the counts of total, working, active, failed, and spare devices.

devicesize

It applies to version 1.1  and  1.2 metadata only (where the metadata is at the start of the device)

and is only useful when the component device has changed size

Remark

 * 用了 "-U byteorder" 後, 直到 DSM 再 mount 它前 check status 都不用 "-e0.9"

    (DSM mount 時會改回 byte-order)

mdadm -E -e0.9 /dev/sdb1

mdadm: No super block found on /dev/sdb1 (Expected magic a92b4efc, got fc4e2ba9)