Re: Checking if RAID does work?

[maarten <maarten@ultratux.net>]

On Wednesday 19 January 2005 22:22, Måns Rullgård wrote:
> maarten <maarten@ultratux.net> writes:
> > To the OP: Yes, every part of a raid-1 array (but only a raid-1
> > array) will / should be mountable and have the same filesystem as
> > the array has.  HOWEVER you should never ever mount the array AT THE
> > SAME TIME as one of its underlying devices!  Always umount first,
> > and only then mount the other.
>
> Furthermore, never ever mount a raid-1 component alone in read-write
> mode.  Modifying the mirrors individually will almost certainly result
> in breakage when the array is activated again.

Speaking from personal experience, I _think_ that modifying a drive that's 
part of an array gets noticed by md (somehow).  At least it always lead to a 
mirror breakage with me, and thus a re-add and a resync was in order.

I'm not sure if it really does that, and neither how it is done, but I'm led 
to believe it does get noticed. Maybe md (or the kernel?) writes a marker 
just before deactivation which signifies "drive was shutdown @..." ?

OTOH, I've also seen that I just modified /etc/fstab on hda1 to reflect that 
not /de/hda1 was root, but /dev/md0 instead, only to find that after a 
reboot /dev/md0 is _indeed_ now mounted as root, but that those recent 
changes in /fstab are gone.  So... maybe I'm just losing my head. (-:

Maarten

-- 

-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html