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List:       linux-ha-dev
Subject:    Re: [Linux-ha-dev] Quorumn device....?
From:       Alan Robertson <alanr () unix ! sh>
Date:       2001-05-30 14:27:23
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Alan Robertson wrote:
> 
> Andy Poling wrote:
> >
> > In a true cluster implementation, this cannot happen.  The shared storage will
> > not let those buffers be flushed to it because that member is no longer
> > eligible to do so (having left - or been ejected from - the cluster).  The
> > write attempts will fail.
> >
> > But your example is probably assuming that the shared disk is not accessed
> > exclusively through the cluster system.  This is a reflection of heartbeat's
> > add-on nature.
> 
> There is no "cluster system" hardware on Linux.  Can't use what's not
> there.  And even when you *do* get your hardware to cooperate, that's called
> I/O fencing.  Stonith is one example of I/O fencing - just as I've said.

IIRC, in VMS clustering, the disks are full cluster members.  So, they
really do have an integrated clustering system.  It's the only one I'm aware
of...  Everyone else makes do with commodity hardware and one of the various
commodity I/O fencing techniques.  I used Stonith because it's very
reliable, and easy to understand.  Other fencing techniques work fine - but
are more difficult to make work on Linux across arbitrary hardware and
software versions.

	-- Alan Robertson
	   alanr@unix.sh
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