Re: grub-probe seems to be having problems

[Lennart Sorensen]

On Fri, Mar 09, 2012 at 07:15:43PM +0100, Vladimir 'φ-coder/phcoder' Serbinenko 
wrote:
> The thing is: raid_disks = 2 in your metadata. I don't know how this
> could be correct or how you could land with such a config.
> @md: The problem is following: Lennart has a raid 1 on 3 disks, however
> raid_disks in sdd2 is 2 and dev_roles contains only [0, 1, -1, -1, ...],
> dev_number is 0
> sda2 and sdb2 contain proper raid_disks=3, dev_roles=[0,1,2,-1,-1,..]
> and dev_number= 0 respectively 1. It looks to me as a seriously damaged
> metadata but apparently mdadm has no problem
> @Lennart: did you dd one disk to another or done something like this?

No.  I did 'dd if=/dev/sda of=/dev/sdd bs=512 count=1' to copy the
partition table, then I did 'hdparm -z /dev/sdd' to reread the partition
table.  I then did 'mdadm --add /dev/md1 /dev/sdd3' to add the final
device to md1 so that it could get raid running fully (I created it with
2/3 devices in degraded mode).  For md0 I added a third raid1 device
just to have all 3 disks able to serve as root even if a disk fails,
and to ensure I could boot no matter what disk failed.

For completeness sake I did actually add /dev/sdc which was an external
USB drive to the raid5 (/dev/md1) first, just to keep the raid safe
until the final internal drive arived.  I then added /dev/sdd3, which
became a hot spare, and then marked sdc3 as faulty, which got the raid
to resync onto the new drive.

> address@hidden:~# mdadm --detail /dev/md0
> /dev/md0:
>         Version : 1.2
>   Creation Time : Wed Feb  8 14:39:24 2012
>      Raid Level : raid1
>      Array Size : 976884 (954.15 MiB 1000.33 MB)
>   Used Dev Size : 976884 (954.15 MiB 1000.33 MB)
>    Raid Devices : 3
>   Total Devices : 3
>     Persistence : Superblock is persistent
> 
>     Update Time : Thu Mar  1 15:02:06 2012
>           State : clean
>  Active Devices : 3
> Working Devices : 3
>  Failed Devices : 0
>   Spare Devices : 0
> 
>            Name : rceng03new:0  (local to host rceng03new)
>            UUID : 88d43dc8:2888fece:34c1486f:49caa398
>          Events : 74
> 
>     Number   Major   Minor   RaidDevice State
>        0       8        2        0      active sync   /dev/sda2
>        1       8       18        1      active sync   /dev/sdb2
>        2       8       50        2      active sync   /dev/sdd2

-- 
Len Sorensen