Date: Fri, 15 Aug 2003 11:53:11 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Pawel Jakub Dawidek <nick@garage.freebsd.pl> Cc: freebsd-hackers@freebsd.org Subject: Re: GEOM Gate. Message-ID: <Pine.NEB.3.96L.1030815114948.94219A-100000@fledge.watson.org> In-Reply-To: <20030815111856.GN395@garage.freebsd.pl>
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On Fri, 15 Aug 2003, Pawel Jakub Dawidek wrote: > On Thu, Aug 14, 2003 at 09:48:57PM +0200, Attila Nagy wrote: > +> Bruce M Simpson wrote: > +> >Whatever next? PCI-over-IP? > +> Collecting cheap on board serial lines to make a big terminal server > +> makes sense to me :) > +> > +> BTW, Pawel's stuff would be even more interesting if it would be > +> possible to mount the same filesystem on more than one machines. > > It'll be, but probably in read-write mode on one machine and read-only > mode on rest machines, because you don't export file systems here, but > disk devices. In order to do this, you need a file system capable of multi-node consistency, and a medium capable of supporting the consistency mechanisms. Since we can't handle mounting the same file system read-write and read-only in multiple places from the same block device without a likely panic, I expect much the same results with a distributed block device. Multiple read-only mounts should work OK, but you don't want to violate the assumptions of the read-only mounts by introducing a read-write mount. File systems can be written that do synchronization on using a protocol of some sort when talking to a common block device, but that will keep you busy for a while, I expect :-). That said, I think the geom gate stuff looks very cool :-). You might be able to run some interesting performance numbers comparing NFS and UFS over a remote block device. Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Network Associates Laboratories
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