gmirror metadata

[Michael Riexinger]

On Thursday 10 March 2005 00:24, Loren M. Lang wrote:
> On Wed, Mar 09, 2005 at 05:43:49PM -0500, Paul Mather wrote:
> > On Wed, 2005-03-09 at 21:22 +0100, Pawel Jakub Dawidek wrote:
> > > On Wed, Mar 09, 2005 at 03:03:33PM +0100, Michael Riexinger
> > > wrote: +> Hi,
> > > +>
> > > +> i have a hp dl320 with an integrated raid controller. I don't
> > > want to +> use that, instead i want to use gmirror. To use the 2
> > > IDE drives, I +> configured 2 raid0 arrays (each with 1 drive) in
> > > the controller's bios. +> Now i wanted to use gmirror, labeled
> > > the second drive. When I did a +> reboot, the raid controller's
> > > bios seems to overwrite the gmirror +> metadata with its own
> > > metadata. Is it impossible to use gmirror witch +> such a
> > > configuration?
> > >
> > > I'll be very odd if controller's BIOS overwrite disk data.
> >
> > Actually, I had the same type of thing happen to me.  I put a LSI
> > MegaRAID IDE 100 that was lying around into my system and attached
> > my existing geom_mirrored drives to it.  I didn't want to use the
> > drives as an ATA RAID, and never set them up as that in the RAID
> > BIOS.  I simply wanted to upgrade from my onboard ATA 33 to the ATA
> > 100 speed the card supported, to get faster disk I/O.
The same type of controller is in the hp dl320 box.

> >
> > To my surprise and regret, my system wouldn't boot properly
> > (couldn't locate the root filesystem) because the ATA RAID card had
> > spammed its metadata over the geom_mirror metadata, and my drives
> > were no longer detected as a geom_mirror.
>
> I believe one difference between this and Micheal's situation is
> that, as I understand it, you created the mirror with a normal ide
> controller, then attached it to the raid controller after that, where
> Micheal labelled it while it was under the raid controller.  A raid
> controller might reserve a sector or track for it's own meta-data,
> but it should still provide a slightly smaller disk that would be
> completely transparent.  You couldn't see the raid controller's
> meta-data sectors nor would any sectors you see or write to be
> modified by the raid controller.
>
The strange thing is: When I labeled the second drive with gmirror and 
rebooted the machine, the raid bios said something like 'new disk 
detected' and rebooted automatically, and then it put it's own metatata 
on it...


Kind regards,

Michael Riexinger
systems engineer

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