Re: RAID-1 does not rebuild after hot-add

[David Chow <davidchow@shaolinmicro.com>]

> Rather than a hex dump, just use
>
>  mdadm --examine /dev/XXX
>
> That is the easiest way to view the superblock on the device.
>
> NeilBrown
Neil,

OK, I find out there is a problem in the superblock which is descrbed as 
follows. The "Total Devices" is wrong. It should be 2 instead of 3. This 
is probably a bug of the mkraid (from raidtools) which when I created 
the array with a "failed-disk" in degraded mode. mkraid incorrectly made 
a wrong superblock even I put "nr-raid-disk 2" and "nr-spare-disks 0" in 
the raidtab. Ok, the superblock is incorrect, but how can I change the 
total devices and spare device pramaters without re-initialize the array?

David Chow

[root@www2 /]# mdadm --examine /dev/sda3
/dev/sda3:
         Magic : a92b4efc
       Version : 00.90.00
          UUID : 39042a54:7c2ca55a:939c1846:94f73fb8
 Creation Time : Sat Aug  2 21:00:17 2003
    Raid Level : raid1
   Device Size : 3076352 (2.93 GiB 3.15 GB)
  Raid Devices : 2
 Total Devices : 3
Preferred Minor : 2

   Update Time : Mon Aug  4 06:25:32 2003
         State : dirty, no-errors
Active Devices : 2
Working Devices : 2
Failed Devices : 1
 Spare Devices : 1
      Checksum : 578aa21 - correct
        Events : 0.15


     Number   Major   Minor   RaidDevice State
this     2       8        3        2        /dev/sda3
  0     0       0        0       -1      faulty
  1     1       8       19        1      active sync   /dev/sdb3
  2     2       8        3        2        /dev/sda3
[root@www2 /]# mdadm --examine /dev/sdb3
/dev/sdb3:
         Magic : a92b4efc
       Version : 00.90.00
          UUID : 39042a54:7c2ca55a:939c1846:94f73fb8
 Creation Time : Sat Aug  2 21:00:17 2003
    Raid Level : raid1
   Device Size : 3076352 (2.93 GiB 3.15 GB)
  Raid Devices : 2
 Total Devices : 3
Preferred Minor : 2

   Update Time : Mon Aug  4 06:25:32 2003
         State : dirty, no-errors
Active Devices : 2
Working Devices : 2
Failed Devices : 1
 Spare Devices : 1
      Checksum : 578aa35 - correct
        Events : 0.15


     Number   Major   Minor   RaidDevice State
this     1       8       19        1      active sync   /dev/sdb3
  0     0       0        0       -1      faulty
  1     1       8       19        1      active sync   /dev/sdb3
  2     2       8        3        2        /dev/sda3


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