From owner-freebsd-fs Fri Jan 31 13: 1:31 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 177AD37B401; Fri, 31 Jan 2003 13:01:30 -0800 (PST) Received: from mcomail02.maxtor.com (mcomail02.maxtor.com [134.6.76.16]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6EB2943F43; Fri, 31 Jan 2003 13:01:29 -0800 (PST) (envelope-from stephen_byan@maxtor.com) Received: from mcoexc03.mlm.maxtor.com (localhost.localdomain [127.0.0.1]) by mcomail02.maxtor.com (8.11.6/8.11.6) with ESMTP id h0VKt3u31068; Fri, 31 Jan 2003 13:55:03 -0700 Received: from mmans02.mma.maxtor.com ([134.6.232.101]) by mcoexc03.mlm.maxtor.com with SMTP (Microsoft Exchange Internet Mail Service Version 5.5.2653.13) id D4XRK8AS; Fri, 31 Jan 2003 14:01:29 -0700 Received: from maxtor.com by mmans02.mma.maxtor.com (8.8.8/1.1.22.3/08May01-0432PM) id QAA0000002604; Fri, 31 Jan 2003 16:01:14 -0500 (EST) Date: Fri, 31 Jan 2003 16:01:13 -0500 Subject: Re: DEV_B_SIZE Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Mime-Version: 1.0 (Apple Message framework v551) Cc: phk@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG, tech-kern@netbsd.org To: David Schultz From: Steve Byan In-Reply-To: <20030131192452.GA15985@HAL9000.homeunix.com> Message-Id: <21B8D16C-355F-11D7-B26B-00306548867E@maxtor.com> Content-Transfer-Encoding: quoted-printable X-Mailer: Apple Mail (2.551) 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 On Friday, January 31, 2003, at 02:24 PM, David Schultz wrote: > If the disk corrupts a sector it was writing, that's already a > problem for us. =46rom the Maxtor Atlas 10K III Product Spec: Section 4.5.1 Power Sequencing You may apply the power in any order or manner, or open either the=20 power or power return line with no loss of data or damage to the disk drive.=20 However, data may be lost in the sector being written at the time of power loss.=20= The drive can withstand transient voltages of +10% to =96100% from nominal while powering up or down. > If the sector is 4K, that just makes it more of a > problem. With FFS and soft updates, we assume that the disk can > atomically write 512 bytes, and we ensure filesystem consistency > by establishing a safe partial ordering for metadata updates. We > expect that after a crash, either the old contents or the new > contents of the sector are there. I think we would need to > implement journalling to ensure integrity if hard drives were > likely to corrupt sectors on power failure. (How often do they do > this right now, and how often would they with 4K sectors?) If you are doing nothing but continuously writing, the active data area=20= covers more than 50% of the track, so you'd have more than a 0.5=20 probability of experiencing a corrupt sector. Derate this by your seek=20= duty-cycle and your write disk utilization to arrive at the final=20 probability. 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