From owner-freebsd-fs Wed Feb 12 21:19:59 2003 Delivered-To: freebsd-fs@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C69AE37B401; Wed, 12 Feb 2003 21:19:57 -0800 (PST) Received: from HAL9000.homeunix.com (12-233-57-224.client.attbi.com [12.233.57.224]) by mx1.FreeBSD.org (Postfix) with ESMTP id A5BB243FAF; Wed, 12 Feb 2003 21:19:56 -0800 (PST) (envelope-from dschultz@uclink.Berkeley.EDU) Received: from HAL9000.homeunix.com (localhost [127.0.0.1]) by HAL9000.homeunix.com (8.12.6/8.12.5) with ESMTP id h1D5JrDm011596; Wed, 12 Feb 2003 21:19:53 -0800 (PST) (envelope-from dschultz@uclink.Berkeley.EDU) Received: (from das@localhost) by HAL9000.homeunix.com (8.12.6/8.12.5/Submit) id h1D5Jqbw011595; Wed, 12 Feb 2003 21:19:52 -0800 (PST) (envelope-from dschultz@uclink.Berkeley.EDU) Date: Wed, 12 Feb 2003 21:19:52 -0800 From: David Schultz To: Brooks Davis Cc: Terry Lambert , Darren Pilgrim , Matthew Emmerton , Daxbert , Bill Moran , Heinrich Rebehn , freebsd-questions@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG Subject: Re: Why is there no JFS? Message-ID: <20030213051952.GA11572@HAL9000.homeunix.com> Mail-Followup-To: Brooks Davis , Terry Lambert , Darren Pilgrim , Matthew Emmerton , Daxbert , Bill Moran , Heinrich Rebehn , freebsd-questions@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG References: <3E4A8EF5.1070308@ant.uni-bremen.de> <3E4A9712.8030609@potentialtech.com> <3E4AA331.5040701@ant.uni-bremen.de> <3E4AA734.5040102@potentialtech.com> <045401c2d2db$f9d45c30$0a0aa8c0@dweebsoft.com> <20030212225631.GA10375@HAL9000.homeunix.com> <005801c2d2eb$aa5fae60$1200a8c0@gsicomp.on.ca> <3E4ADDDE.5040208@pantherdragon.org> <3E4B138F.26E32E75@mindspring.com> <20030212210721.A9481@Odin.AC.HMC.Edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030212210721.A9481@Odin.AC.HMC.Edu> Sender: owner-freebsd-fs@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org Thus spake Brooks Davis : > On Wed, Feb 12, 2003 at 07:40:00PM -0800, Terry Lambert wrote: > > Darren Pilgrim wrote: > > > Not really. A properly laid-out filesystem hierarchy will result in no > > > writes to / (except for installworld/kernel). That removes the problem > > > that journalling addresses, and is probably why softupdates is disabled > > > by default for /. For large, active filesystems, journalling would be a > > > big improvement when you had to run a foreground fsck. > > > > Soft updates are disable on / by default because of the chicken > > and egg problem of runing tunefs on /. > > There's no chicken and egg problem when you're booting off install > media or for that matter from single user mode. The problem was that > softupdates means you don't get space back from deleted files immediatly > so previously / tended to fillup during installworld or installkernel. > I know some fixes have been implemented in that area, but I'm not sure > if then mean you can always write to the space occupied by unlinked > files or just that you have a better chance. The problem is effectively fixed in 5.0. Basically, when no space can be found, the syncer is accelerated to try to speed up frees. Technically it's possible to run into a livelock, where you keep freeing space and it keeps getting snatched up before you can grab it, so you wait forever. So IIRC, there is a point where it just gives up on finding the space. However, that won't happen with an install, so the free space problem isn't a reason not to use softupdates on the root FS. I think the default hasn't been changed just because nobody has bothered. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message