Re: Problem rebuild raid 1 replacement disk

[NeilBrown <neilb@suse.de>]

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On Mon, 20 Feb 2012 18:58:22 +1030 "RANSOM, Tony"
<tony.ransom@baesystems.com> wrote:

> Neil,
> 
> Thanks for the reply:
> 
> 
> >What is the output of each of
> >  mdadm -E /dev/sdb
> 
> root@server2:~# mdadm -E /dev/sdb
> /dev/sdb:
>           Magic : a92b4efc
>         Version : 00.90.00
>            UUID : 15e5ad84:82b4dd79:6719eb14:a41dd719
>   Creation Time : Mon Mar 28 23:52:08 2011
>      Raid Level : raid1
>   Used Dev Size : 1953027008 (1862.55 GiB 1999.90 GB)
>      Array Size : 1953027008 (1862.55 GiB 1999.90 GB)
>    Raid Devices : 2
>   Total Devices : 2
> Preferred Minor : 1
> 
>     Update Time : Sun Feb 19 15:44:55 2012
>           State : active
>  Active Devices : 1
> Working Devices : 2
>  Failed Devices : 0
>   Spare Devices : 1
>        Checksum : 5e4b8288 - correct
>          Events : 1314601
> 
>       Number   Major   Minor   RaidDevice State
> this     2       8       16        2      spare   /dev/sdb
> 
>    0     0       0        0        0      removed
>    1     1       8        3        1      active sync   /dev/sda3
>    2     2       8       16        2      spare   /dev/sdb
> 
> 
> >  mdadm -E /dev/sdb3
> 
> root@server2:~# mdadm -E /dev/sdb3
> /dev/sdb3:
>           Magic : a92b4efc
>         Version : 00.90.00
>            UUID : 15e5ad84:82b4dd79:6719eb14:a41dd719
>   Creation Time : Mon Mar 28 23:52:08 2011
>      Raid Level : raid1
>   Used Dev Size : 1953027008 (1862.55 GiB 1999.90 GB)
>      Array Size : 1953027008 (1862.55 GiB 1999.90 GB)
>    Raid Devices : 2
>   Total Devices : 2
> Preferred Minor : 1
> 
>     Update Time : Mon Feb 20 18:38:09 2012
>           State : clean
>  Active Devices : 2
> Working Devices : 2
>  Failed Devices : 0
>   Spare Devices : 0
>        Checksum : 5e621af4 - correct
>          Events : 1349308
> 
> 
>       Number   Major   Minor   RaidDevice State
> this     0       8       19        0      active sync   /dev/sdb3
> 
>    0     0       8       19        0      active sync   /dev/sdb3
>    1     1       8        3        1      active sync   /dev/sda3
> 
> 
> 
> 
> >What version of mdadm do you have?
> 
> root@server2:~# mdadm -V
> mdadm - v2.6.7.1 - 15th October 2008
> 
> >What is the starting sector of /dev/sdb3?  In particular, is it a multiple of
> 64K?
> 
> 589824
> 
> Doesn't appear to be. Each sector (according to gdisk is 512 bytes), but this is same as sda.
> 
> 
> Odd that the system thinks sdb is a spare?
> 
> Can it be corrected?

Yes.
Somehow both sdb and sdb3 have a superblock for the same array.  Must have
been a typo somewhere I suspect.
You should remove the one you don't want:

  mdadm --zero-superblock /dev/sdb

then it should all work nicely again.

(if the offset is a multiple of 64K you can get the both having exactly the
same superblock (same location on disk).  Newer versions of mdadm try to help
you catch that case, older versions don't.  But that doesn't seem to be an
issue for you).

NeilBrown

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