From owner-freebsd-stable Mon Aug 19 9: 4:18 2002 Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 32E2237B405 for ; Mon, 19 Aug 2002 09:04:14 -0700 (PDT) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id B793D43E72 for ; Mon, 19 Aug 2002 09:04:13 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.12.5/8.12.4) with ESMTP id g7JG4Ddc077233 for ; Mon, 19 Aug 2002 09:04:13 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.12.5/8.12.4/Submit) id g7JG4DOU077232; Mon, 19 Aug 2002 09:04:13 -0700 (PDT) (envelope-from dillon) Date: Mon, 19 Aug 2002 09:04:13 -0700 (PDT) From: Matthew Dillon Message-Id: <200208191604.g7JG4DOU077232@apollo.backplane.com> To: freebsd-stable@FreeBSD.ORG Subject: Re: root (/) not soft-updates by default ? References: <20020819144928.GA6628@nebula.wanadoo.fr> <20020819105452.A14530@blackhelicopters.org> Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG This conversation is moot, since modern IDE drives (and apparently seeping into SCSI drives as well) do track-at-once writes to the physical media, there is no ordering guarentee no matter what you do, and IDE performance with write caching turned off sucks so badly you pretty much *have* to turn it on if tags are not supported or suffer penalties so severe that the last time we tried it our user community was up in arms over the result. So short of caching the data in NVRAM you are *screwed* no matter what you do. Oh, wait, even caching the data in NVRAM doesn't save us, since track-at-once writes rewrite sectors we never modified. So we might as well turn write caching on. If you don't like the default, you can turn it off in /boot/loader.conf. In any case, Jaime Bozza's explanation (the smallish root can fill up with softupdates enabled when installing a new system over the old one) is the correct one. This issue is fixed in -current's softupdates but not fixed in -stable's. The business about IDE not ordering writes is also correct, but the statement that softupdates is somehow *worse* then a normal mount with an IDE disk is not correct. Both are equally dangerous due to the track-at-once writes which IDE drives tend to do these days. Since very little on the root partition is modified once a system has come up, not enabling softupdates on root is not a big deal. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message