[Gllug] Replacement SATA disk naming

[Alain Williams]

On Thu, Mar 05, 2009 at 11:57:17PM +0000, Nix wrote:
> On 5 Mar 2009, Bruce Richardson outgrape:
> 
> > On Thu, Mar 05, 2009 at 03:07:09PM +0000, Alain wrote:
> >> 
> >> I created links sda* -> sdc* .... but the mirroring stuff looks through that
> >> to the device numbers:
> >> 'mdadm --query --detail /dev/md0' reports:
> >
> > Are you sure it's tied to the device numbers of the underlying devices?
> > I thought it put a superblock into each device which uniqely identifies
> > each device in each array.  This should survive a reboot.
> 
> This depends on how /etc/mdadm.conf is laid out. If it says (as is
> recommended) something like
> 
> DEVICE partitions
> ARRAY /dev/md0 UUID=3a51b74f:8a759fe7:8520304c:3adbceb1
> ARRAY /dev/md1 UUID=a5a6cad4:2c7fdc07:88a409b9:192ed3bf
> ARRAY /dev/md2 UUID=fe44916d:a1098576:8007fb81:2ee33b5a
> [...]
> 
> then it will use the UUIDs of the arrays and devices to assemble
> everything in the correct order. If it names underlying block devices
> explicitly, you could see it assembling things in the wrong order if
> device names change (which would be disastrous).

man 4 md -- explains that, yes, the UUID is important and what is used, good.

Things have become more interesting: I was copying the 'good' disk to the newly
inserted disk to have it fail - with bad blocks on the 'good' disk; however the system
still seems quite happy so I susupect that the bad blocks are 'in between' files
or 'unimportant' files. I am getting a bad block list to see where the errors
are ... it is getting close to time for a complete OS reinstall :-(

User data is safe - thankfully

-- 
Alain Williams
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