[CentOS] CentOS 4 Software Raid1 questions

Fri Apr 29 18:52:18 UTC 2005
Les Mikesell <lesmikesell at gmail.com>

On Fri, 2005-04-29 at 13:18, Aleksandar Milivojevic wrote:

> > If you
> > have both, I'm not sure which wins.  If you find documentation
> > on the detection order or how to move devices, please post
> > a link.
> The kernel wins.  As soon as raid* device drivers are loaded (for 
> example, from initrd image, waaaay before even root file is mounted), 
> they'll do the automagic stuff.  The system will spit warnings later if 
> information in mdadm.conf is contradicting.

Thanks, now what happens when you move a set built on one machine
to a different machine, or if you move drives intending to reformat
but end up with mismatched members that are detected at bootup.
I remember having a disaster years ago when I tried to minimize
downtime by building a raid1 set on a different machine and
pre-loading files, then shutting down just long enough to swap
the drive in place.  I think they were either paired with the
wrong mates or the md? devices were detected in the wrong order
as the machine rebooted.  Maybe this has been fixed in the newer
kernel versions but since then I've gone out of my way to avoid
repeating the situation - sometimes as far as low-leveling on a
non-production machine before moving a drive that may have been
part of a raid or even one that might have a conflicting partition

  Les Mikesell
    les at futuresource.com