From owner-freebsd-questions@FreeBSD.ORG Sat Apr 19 18:05:11 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B508D1065671 for ; Sat, 19 Apr 2008 18:05:11 +0000 (UTC) (envelope-from fbsd.questions@rachie.is-a-geek.net) Received: from snoogles.rachie.is-a-geek.net (rachie.is-a-geek.net [66.230.99.27]) by mx1.freebsd.org (Postfix) with ESMTP id 570978FC1A for ; Sat, 19 Apr 2008 18:05:11 +0000 (UTC) (envelope-from fbsd.questions@rachie.is-a-geek.net) Received: from localhost (localhost [127.0.0.1]) by snoogles.rachie.is-a-geek.net (Postfix) with ESMTP id 97FD31CC91; Sat, 19 Apr 2008 10:05:09 -0800 (AKDT) From: Mel To: freebsd-questions@freebsd.org Date: Sat, 19 Apr 2008 20:05:05 +0200 User-Agent: KMail/1.9.7 References: <790871.1688.qm@web57004.mail.re3.yahoo.com> <9bbcef730804180840y77adff73x7ad0cf90c82633a9@mail.gmail.com> In-Reply-To: <9bbcef730804180840y77adff73x7ad0cf90c82633a9@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200804192005.06962.fbsd.questions@rachie.is-a-geek.net> Cc: Ivan Voras Subject: Sidetracked: why gjournal over soft-updates (Was: Re: UFS2 Journaling implementation detail) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 19 Apr 2008 18:05:11 -0000 On Friday 18 April 2008 17:40:04 Ivan Voras wrote: > > 5. "Some UFS implementations avoid journaling and > > instead implement soft updates: they order their > > writes in such a way that the on-disk file system is > > never inconsistent, or that the only inconsistency > > that can be created in the event of a crash is a > > storage leak. To recover from these leaks, the free > > space map is reconciled against a full walk of the > > file system at next mount." - > > (http://en.wikipedia.org/wiki/Journaling_file_system) > > > > So the disadvantage of Soft Update is it is necessary > > to run fsck after reboot in event of a crash or power > > failure? > > Yes. The advantage is that practically, the data is as safe as with > journalling. I've been following this with interest, however it's still not clear to me, why I'd want a journaling filesystem, because: 1) If you have soft-updates the data is as safe as with journal 2) If you have soft-updates fsck will run in the background 3) Soft-updates don't require diskspace. So...other then "journaling filesystems are cool", what's the real advantage? -- Mel Problem with today's modular software: they start with the modules and never get to the software part.