[CentOS] doing a new install on top of existing software raid-1

Les Mikesell lesmikesell at gmail.com
Sun Jan 22 04:52:33 UTC 2012

On Sat, Jan 21, 2012 at 9:49 PM, Gordon Messmer <yinyang at eburg.com> wrote:
> On 01/21/2012 05:52 PM, Les Mikesell wrote:
>> I have moved raid sets to other machines (of similar distribution
>> revs) and never had a problem before.
> I wouldn't expect you to.  If you move volumes other than the boot
> volume, it doesn't matter that they get a new device name.
>> In fact I have fairly regularly
>> split raid1 volumes to different machines and re-synced with new
>> mirrors and never had any surprises before.  The real issue with this
>> box was that the disks are all swappable and I had used raid with
>> autodetect specifically so I didn't have to track which disk was
>> where.   And after booting the live dvd, they became more or less
>> randomly named md devices, with each disk of the set becoming its own
>> md device instead of pairing.  Recovering was fairly painful.
> Well, you haven't given us enough information to really explain what you
> saw.  What I'd expect is that your MD devices were moved to /dev/md126,
> /dev/md127, etc.  Those names aren't random; they're sequential,
> reflecting the assigned device minor number starting at minor number
> 126.  "dmesg" output might explain why the RAID sets weren't
> assembled... I've never seen that happen.

Yes, they were renamed with those unexpected names.  I didn't really
spend much time figuring it out, since I thought things would work
normally when rebooted with the existing 5.x system.  They didn't -
the new names stuck, including the ones given to the 'other half' of
each mirror.

   Les Mikesell
      lesmikesell at gmail.com

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