From owner-freebsd-questions Thu Feb 13 16: 1:53 2003 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8E4EB37B401; Thu, 13 Feb 2003 16:01:51 -0800 (PST) Received: from stork.mail.pas.earthlink.net (stork.mail.pas.earthlink.net [207.217.120.188]) by mx1.FreeBSD.org (Postfix) with ESMTP id D005A43F85; Thu, 13 Feb 2003 16:01:50 -0800 (PST) (envelope-from tlambert2@mindspring.com) Received: from pool0247.cvx22-bradley.dialup.earthlink.net ([209.179.198.247] helo=mindspring.com) by stork.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128) (Exim 3.33 #1) id 18jTIU-0004yH-00; Thu, 13 Feb 2003 16:01:43 -0800 Message-ID: <3E4C3195.FAB92EEA@mindspring.com> Date: Thu, 13 Feb 2003 16:00:21 -0800 From: Terry Lambert X-Mailer: Mozilla 4.79 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: David Schultz Cc: Darren Pilgrim , Brooks Davis , Matthew Emmerton , Daxbert , Bill Moran , Heinrich Rebehn , freebsd-questions@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG Subject: Re: Why is there no JFS? References: <005801c2d2eb$aa5fae60$1200a8c0@gsicomp.on.ca> <3E4ADDDE.5040208@pantherdragon.org> <3E4B138F.26E32E75@mindspring.com> <20030212210721.A9481@Odin.AC.HMC.Edu> <20030213051952.GA11572@HAL9000.homeunix.com> <3E4B467B.4DCF6D5@mindspring.com> <20030213074449.GA12084@HAL9000.homeunix.com> <3E4BA1D2.E259308@mindspring.com> <20030213191356.GA14560@HAL9000.homeunix.com> <3E4BFE74.2000103@pantherdragon.org> <20030213211123.GA15047@HAL9000.homeunix.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a4e6e963775cab5cb297c3d1cb5f9747c3a7ce0e8f8d31aa3f350badd9bab72f9c350badd9bab72f9c Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG David Schultz wrote: > > I think softupdates is still (viewed as) riskier than synchronous > > writes, at least for large numbers of writes (like installworld) to a NB: An initial system install is done with async mounts. You can't use async mounts if you use soft updates, because the dependencies for already outstanding pending writes won't be there after a "mount -u". Same is true of sync mounts, but install doesn't use that, or try to use "mount -u". > I've heard that argument, and while I think it has *some* validity > in general, I don't buy it for installworld/installkernel in > particular. Softupdates guarantees metadata consistency (modulo > hardware issues that have been discussed on this list before), but > it can reorder writes and delay the amount of time it takes your > data to hit the disk. For an installworld, this means that the > window during which you have a partially installed world is > slightly larger, but installworld takes a while, so the window is > already pretty darn big. The whole rationale for doing > installworld/installkernel in a particular sequence is that with > any luck, you can boot to single-user mode after something goes > wrong and finish the job (or revert to the old kernel.) Heh. This is the "Lightning is less likely to hit me if I play golf very fast, even though I'm doing it in a thunderstorm" argument. It's based on a false understanding of statistics, and it's the same argument Linux FS people used to use, back before they had an FS that ordered metadata writes, to justify not ordering metadata writes (e.g. "use async, the failure window is smaller"). And we all know that's really bogus. 8-) 8-). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message