From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Becker Subject: Re: [RFC 0/13] extents and 48bit ext3 Date: Fri, 9 Jun 2006 13:38:03 -0700 Message-ID: <20060609203803.GF3574@ca-server1.us.oracle.com> References: <4488E1A4.20305@garzik.org> <20060609083523.GQ5964@schatzie.adilger.int> <44898EE3.6080903@garzik.org> <448992EB.5070405@garzik.org> <4489A7ED.8070007@garzik.org> <20060609195750.GD10524@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: To: Theodore Tso , Jeff Garzik , Alex Tomas , Andrew Morton , ext2-devel , linux-kernel@vger.kernel.org, Linus Torvalds , cmm@us.ibm.com, linux-fsdevel@vger.kernel.org, Andreas Dilger Content-Disposition: inline In-Reply-To: <20060609195750.GD10524@thunk.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ext2-devel-bounces@lists.sourceforge.net Errors-To: ext2-devel-bounces@lists.sourceforge.net List-Id: linux-fsdevel.vger.kernel.org On Fri, Jun 09, 2006 at 03:57:50PM -0400, Theodore Tso wrote: > We don't do this with the SCSI layer where we make a complete clone of > the driver layer so that there is a /usr/src/linux/driver/scsi and > /usr/src/linux/driver/scsi2, do we? And we didn't do that with the > networking layer either, as we added ipsec, ipv6, softnet, and a whole > host of other changes and improvements. Ted, We don't have any permanent, physical representation of the state either. With a filesystem we do. I don't care how many changes you made to the SCSI stack. The code from a year ago could be entirely different. However, if the old stack and the new stack both support card X, then it Just Works. The Adaptec driver is a case in point. When the new driver was still flaky, folks and distros could select the old driver with impunity. Running the new driver didn't fundamentally change your Adaptec card so you couldn't run the old one. Filesystem features are different. There is a permanent state that the older code cannot read. Alex claims people just shouldn't use "-o extents", but the fact is their distro will choose it for them. We have multiboot machines in our test lab, because like many people we don't have unlimited funds. What happened when we installed the 2.6 distros? All of a sudden the older 2.4 distros wouldn't mount the shared filesystems, becuase of ext3 features. This wasn't the kernel driver, this was merely the tools! Surprise! We made no choice to use new features, and they were thrust upon us. This will happen to others. Joel -- "Sometimes one pays most for the things one gets for nothing." - Albert Einstein Joel Becker Principal Software Developer Oracle E-mail: joel.becker@oracle.com Phone: (650) 506-8127