mismatch_cnt != 0, member content mismatch, but md says the mirror is good

[Benjamin Scott]

On Sun, Feb 21, 2010 at 4:26 PM, Shawn O'Shea <shawn at eth0.net> wrote:
> I know I'm resurrecting an old thread here, but I just saw a post in Planet
> CentOS that seems to have some info on fixing the mismatch_cnt is no 0
> error, Take a loog at this blog post where the author's suggests some md
> actions that can be taken to clear these errors:
> http://www.arrfab.net/blog/?p=199

  Right.  In short, run a repair on the mirrors.  I saw someone give
advice before.  My issue is, the only way I know of for a simple
mirror to be repaired is to arbitrarily declare one of the members the
"good" copy, and copy it all to the other member.  Is that what the
kernel RAID driver does?  If so, how does it decide which member is
the good copy?  is there any way to influence that decision?

  And none of this answers the questions of how it happened in the
first place, nor how it was detected.

  If this is due to GRUB being installed individually on to each
mirror member (by booting from floppy), then I suspect copying one
mirror member to the other is actually the *wrong* thing to do, since
you'll clobber the second disk's unique GRUB installation with the one
from the first disk (presumably, the first disk's GRUB won't work on
the second disk).

-- Ben