From owner-freebsd-hackers@FreeBSD.ORG Fri Aug 15 08:53:47 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 502D537B401 for ; Fri, 15 Aug 2003 08:53:47 -0700 (PDT) Received: from fledge.watson.org (fledge.watson.org [204.156.12.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8731843F93 for ; Fri, 15 Aug 2003 08:53:46 -0700 (PDT) (envelope-from robert@fledge.watson.org) Received: from fledge.watson.org (localhost [127.0.0.1]) by fledge.watson.org (8.12.9/8.12.9) with ESMTP id h7FFrCAL002129; Fri, 15 Aug 2003 11:53:12 -0400 (EDT) (envelope-from robert@fledge.watson.org) Received: from localhost (robert@localhost)h7FFrBQZ002126; Fri, 15 Aug 2003 11:53:11 -0400 (EDT) Date: Fri, 15 Aug 2003 11:53:11 -0400 (EDT) From: Robert Watson X-Sender: robert@fledge.watson.org To: Pawel Jakub Dawidek In-Reply-To: <20030815111856.GN395@garage.freebsd.pl> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: Buckie cc: freebsd-hackers@freebsd.org Subject: Re: GEOM Gate. X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Aug 2003 15:53:47 -0000 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