[CentOS] *very* ugly mdadm issue [Solved, badly]

Thu Sep 4 20:48:49 UTC 2014
m.roth at 5-cent.us <m.roth at 5-cent.us>

Tom Bishop wrote:
> On Thu, Sep 4, 2014 at 3:30 PM,  <m.roth at 5-cent.us> wrote:
>>    Here's the answer: making a software RAID on a bare drive with no GPT
>> works fine. If it has a GPT, and no partition, it fails on reboot, even
>> with an /etc/mdadm.conf.
>>    I've proved this:
>>        first, I created the array on the bare drive, rebooted, and
>> /dev/md0 was there;
>>        then, I used parted to create a gpt, then the array, reboot, no
>> md0, even with mdadm --assemble, even with /etc/mdadm.conf.
>>        finally, I got rid of the disk label (parted to make an msdos
>> label, the zeroing out the beginning of the disk), and again made
>> the RAID on the bare drives, reboot, and md0 is there.
>>    So that's what killed me. Admins, take heed....
> Thanks for the followup.
> :)

Yup. My manager had asked me to figure it out, and as it just so happened
our director wound up needing more space on another machine, that I could
reboot as I will, I could do the testing.

         mark, watch out for the gotchas