From owner-freebsd-hackers Mon Oct 28 21:41:49 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7969237B401 for ; Mon, 28 Oct 2002 21:41:48 -0800 (PST) Received: from aaz.links.ru (aaz.links.ru [193.125.152.37]) by mx1.FreeBSD.org (Postfix) with ESMTP id 93C5B43E4A for ; Mon, 28 Oct 2002 21:41:47 -0800 (PST) (envelope-from babolo@aaz.links.ru) Received: from aaz.links.ru (aaz.links.ru [193.125.152.37]) by aaz.links.ru (8.12.6/8.12.6) with ESMTP id g9T5gJDh036717; Tue, 29 Oct 2002 08:42:19 +0300 (MSK) (envelope-from babolo@aaz.links.ru) Received: (from babolo@localhost) by aaz.links.ru (8.12.6/8.12.6/Submit) id g9T5g6PV036712; Tue, 29 Oct 2002 08:42:06 +0300 (MSK) Message-Id: <200210290542.g9T5g6PV036712@aaz.links.ru> Subject: Re: [hardware] Tagged Command Queuing or Larger Cache ? X-ELM-OSV: (Our standard violations) hdr-charset=KOI8-R; no-hdr-encoding=1 In-Reply-To: <20021029042415.967662A88D@canning.wemm.org> To: Peter Wemm Date: Tue, 29 Oct 2002 08:42:05 +0300 (MSK) From: "."@babolo.ru Cc: "Daniel O'Connor" , Chuck Robey , Kenneth Culver , "Wilkinson, Alex" , hackers@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL99b (25)] MIME-Version: 1.0 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > "Daniel O'Connor" wrote: > As you can imagine, this violates the basic assumptions of FFS and softdep. > They assume that only sectors that are written to are at risk, and do all > their ordering based on that assumption. But the assumption is completely > bogus. Even with no-caching it doesn't work because if the drive loses > power after only having written half of the track, then you risk losing the > rest - the track is written from "wherever", and not any index marks. ie: > the track is just as likely to overwrite the second half of the sectors > first, and when you lose power, you have two copies of the first half of > the sectors. Basically you have to assume that the entire track and > all of the nearby sectors could get lost or trashed. I usually lose 4..8 sectors cluster on fast power down on IBM IDE drives. Repairable. -- @BABOLO http://links.ru/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message