[CentOS] *very* ugly mdadm issue

[Les Mikesell]

On Thu, Sep 4, 2014 at 9:59 AM, Lamar Owen <lowen at pari.edu> wrote:
>
>>
> Of course; but in the context of an MD RAID device with member devices as
> raw disks I would not expect a partition table of any kind, GPT or
> otherwise.  Whether it can be there or not is not my point; it's whether
> it's expected or not.
>
> Now, for C6 the default RAID superblock is version 1.2; but if you were to
> create a version 1.1 superblock it would go on the very first sector of the
> raw device, and would overwrite the partition table.  (The 1.2 superblock
> goes 4K in from the first sector; prior to 1.1 the superblock went to the
> last sector of the drive).

Does that mean autodetection/assembly would be possible with 1.2 but
not 1.1?  I've always considered that to be one of the best features
of software raid.

> Of course, ext4 at least for block group 0 skips the first 1k bytes.....

How does this mesh with the ability to mount a RAID1 member as a
normal non-raid partition?   I've done that for data recovery but
never knew if it was safe to write that way.

-- 
  Les Mikesell
    lesmikesell at gmail.com