[CentOS] md boot device

Les Mikesell lesmikesell at gmail.com
Wed Jan 27 04:36:59 UTC 2010

Joseph L. Casale wrote:
> The secondary disc was used in a lab rig to boot off of and test something
> after which the primary was replaced and the system was booted off of. It
> saw the secondary as more recent and dropped the primary so, the secondary was
> removed and the primary was used to boot.
> Figuring that made it more recent, even after it was restarted with the "now
> older" secondary, it still wants to drop the primary?
> W/o blowing out the secondary (it can't be hot added) how can I force the
> primary to not be dropped? I'm amused that even with it used to boot solo,
> and hence timestamps validating it as most recent, md will only use the
> secondary to start from?

Unless there is something on the primary that you need to keep, just re-sync 
from the active partition and next time they will come up paired:
mdadm --add md_device missing_partition
cat /proc/mdstat to see the status

If you need to keep something on the primary, remove the secondary and reboot 
several times.  I think there is a count of clean shutdowns that is used to 
determine if one is more current than the other - maybe there is a more 
intelligent way to update it, though.  Then when you get the right one active, 
sync to the other.

   Les Mikesell
    lesmikesell at gmail.com

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