From owner-freebsd-fs Fri Jan 31 11:11:31 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 923CE37B405; Fri, 31 Jan 2003 11:11:29 -0800 (PST) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1615F43F9B; Fri, 31 Jan 2003 11:11:28 -0800 (PST) (envelope-from bright@elvis.mu.org) Received: by elvis.mu.org (Postfix, from userid 1192) id DEA1AAE1C1; Fri, 31 Jan 2003 11:11:27 -0800 (PST) Date: Fri, 31 Jan 2003 11:11:27 -0800 From: Alfred Perlstein To: Steve Byan Cc: David Laight , phk@freebsd.org, freebsd-fs@freebsd.org, tech-kern@netbsd.org Subject: Re: DEV_B_SIZE Message-ID: <20030131191127.GS85104@elvis.mu.org> References: <20030131185507.G1487@snowdrop.l8s.co.uk> <538478DE-354E-11D7-B26B-00306548867E@maxtor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <538478DE-354E-11D7-B26B-00306548867E@maxtor.com> User-Agent: Mutt/1.4i 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 I hope I'm not mistaken here, but for FFS to work it needs the 512 byte ops to be atomic, making them not so, or possibly obliterate surrounding blocks doesn't sound like a good idea at all. Shouldn't you guys be asking Dr McKusick? I can forward this question on to some of the fs people at Apple as well. * Steve Byan [030131 11:01] wrote: > > On Friday, January 31, 2003, at 01:55 PM, David Laight wrote: > > >>Really? fsck can recover from losing 4K bytes surrounding the last > >>metadata block written? > > > >The only metadata that matter are the inodes and (for ffs) the > >indirect blocks. You do really want the latter to be single disk > >blocks - many systems actually write them synchonously. > > What could be the effect of losing surrounding blocks on the (failed) > write of an indirect block? Can we guarantee that fsck can reconstruct > the filesystem, modulo some recently-created or deleted files, or is > there a possibility of losing the entire filesystem? > > >The inode is (probably) only 128 bytes, losing an inode block > >will lose the other files. > > > >A journaling filesystem probably already has ways around this... > > I think journaling filesystems need to know the atomic block size in > order to structure their log in a fault-tolerant way; I'm hoping > someone on these lists can provide some details. > > Regards, > -Steve > -------- > Steve Byan > Design Engineer > Maxtor Corp. > MS 1-3/E23 > 333 South Street > Shrewsbury, MA 01545 > (508) 770-3414 > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-fs" in the body of the message -- -Alfred Perlstein [alfred@freebsd.org] 'Instead of asking why a piece of software is using "1970s technology," start asking why software is ignoring 30 years of accumulated wisdom.' To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message