From owner-freebsd-fs Fri Jan 31 11:22:13 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 A553D37B401 for ; Fri, 31 Jan 2003 11:22:11 -0800 (PST) Received: from mcomail02.maxtor.com (mcomail02.maxtor.com [134.6.76.16]) by mx1.FreeBSD.org (Postfix) with ESMTP id E75FE43F43 for ; Fri, 31 Jan 2003 11:22:10 -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 h0VJFkc31069; Fri, 31 Jan 2003 12:15:46 -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 D4XRKZHS; Fri, 31 Jan 2003 12:22:09 -0700 Received: from maxtor.com by mmans02.mma.maxtor.com (8.8.8/1.1.22.3/08May01-0432PM) id OAA0000002265; Fri, 31 Jan 2003 14:21:51 -0500 (EST) Date: Fri, 31 Jan 2003 14:21:49 -0500 Subject: Re: DEV_B_SIZE Content-Type: text/plain; charset=US-ASCII; format=flowed Mime-Version: 1.0 (Apple Message framework v551) Cc: , To: From: Steve Byan In-Reply-To: <001601c2c95a$63d52d70$0300a8c0@jkirbydesk> Message-Id: <3F18DF97-3551-11D7-B26B-00306548867E@maxtor.com> Content-Transfer-Encoding: 7bit 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 01:55 PM, Jamey Kirby wrote: > I have been a lurker for years and want to chime in. Hi Jamey, recognize your name from the NTFS list. > Under Windows NT (all flavors), using a 4K sector size works fine. The > OS abstraction layers are very good and handling the alignment. Yes, I've seen the code in the DDK and in the filesystem developers kit. NT's SCSI driver is already properly parameterized to use the block size returned by the device, as long as it is a power of 2 and greater than 512 byte. However, I wonder about the failure semantics assumed by NTFS's log - does it rely on the beginning and the ending of each log record being in different physical sectors? Does it rely on no more than one sector being lost at the end of the log (i.e. could wiping out 4K at the tail of the log wipe out enough state such that the recovery code couldn't roll-back/roll-forward to a consistent filesystem state)? How about the ExchangeServer? Does it's transaction mechanism depend on a specific block size? How about SQLServer? My concern is that a backwards-compatibility mechanism is being proposed that makes a device (even a SCSI device) with 4K physical blocks look like a 512-byte block device. I fear that since the failure semantics are subtly different, the careful-write and persistent logging strategies in current code will break, and no one will know until they experience the corner condition that results in their {filesystem | database | email server | transaction processing monitor} losing their data. 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