From owner-freebsd-questions Wed Jan 30 12:22:13 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mail7.nc.rr.com (fe7.southeast.rr.com [24.93.67.54]) by hub.freebsd.org (Postfix) with ESMTP id D2E4137B435 for ; Wed, 30 Jan 2002 12:21:44 -0800 (PST) Received: from i8k.babbleon.org ([66.57.85.154]) by mail7.nc.rr.com with Microsoft SMTPSVC(5.5.1877.687.68); Wed, 30 Jan 2002 14:15:50 -0500 Received: by i8k.babbleon.org (Postfix, from userid 111) id 323464078; Wed, 30 Jan 2002 14:14:39 -0500 (EST) Content-Type: text/plain; charset="iso-8859-1" From: Brian T.Schellenberger To: Espen Tagestad , questions@FreeBSD.ORG Subject: Re: Softupdates Date: Wed, 30 Jan 2002 14:14:38 -0500 X-Mailer: KMail [version 1.3] References: <3C593C4A@epostleser.online.no> <20020130124756.A15728@modula.no> In-Reply-To: <20020130124756.A15728@modula.no> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <20020130191439.323464078@i8k.babbleon.org> Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Wednesday 30 January 2002 06:47 am, Espen Tagestad wrote: > On Wed, Jan 30, 2002 at 12:34:11PM +0100, Christer Gundersen wrote: > > As i read the RELEASE NOTES, i see that SOFTUPDATES will be activated by > > default under install. but it also says that it will not enable > > SOFTUPDATES on the root ( / ) fs . why? is that bad? > > Because with SoftUpdates read/write operations often delay, sometimes > up to 30 seconds before it's done. Then, if a machine crash occurs it > may lead to a larger loss of data. That can cause unrecoverable damage > to your system. As long as you turn off write caching, this isn't true (if it were true, then softupdates would be a disaster for *all* filesystems, not just root). That is, things may be delayed but they are in a consistent state at all times, and never corrupt. At worst, the last files you deleted will "undelete" themselves and the last files you created may not be there, but no file-system corruption will occur. Now it IS a bad idea (even though many people do it without happening to get burned) to run with write caching *and* softupdates both on. In general, it's a bad isea to run with write caching, period, but combining it with softupdates makes things a lot worse, but softupdates without write caching is safer than the other way 'round. Of course, turning both off is safest and slowest, so pick your poison. I use softupdates on ALL file systems and turn off write caching myself. (To turn off write-caching, put this in /boot/loader.conf: # write cache considered dangerous hw.ata.wc=0 ) The reason for the general advice to turn it off on / is because it does introduce a delay and / is traditionally rather small. The delay effectively gives you less space in a file system since freed space may not be freed yet, but if you make / larger than usual and turn on softupdates you'll get the speed benefit of softupdates and yet won't risk running out of disk space. (It seems an especial shame to turn off softupdates on whatever file system contains /tmp since the benefits are larger on a file system with lots of writes.) > > > regards, > > Espen Tagestad > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message -- Brian T. Schellenberger . . . . . . . bts@wnt.sas.com (work) Brian, the man from Babble-On . . . . bts@babbleon.org (personal) ME --> http://www.babbleon.org http://www.eff.org <-- GOOD GUYS --> http://www.programming-freedom.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message