From owner-freebsd-stable Mon Mar 12 14: 7:59 2001 Delivered-To: freebsd-stable@freebsd.org Received: from fw.wintelcom.net (ns1.wintelcom.net [209.1.153.20]) by hub.freebsd.org (Postfix) with ESMTP id 3966637B719; Mon, 12 Mar 2001 14:07:54 -0800 (PST) (envelope-from bright@fw.wintelcom.net) Received: (from bright@localhost) by fw.wintelcom.net (8.10.0/8.10.0) id f2CM6at22778; Mon, 12 Mar 2001 14:06:36 -0800 (PST) Date: Mon, 12 Mar 2001 14:06:36 -0800 From: Alfred Perlstein To: Kevin Oberman Cc: Soren Schmidt , mobile@FreeBSD.ORG, stable@FreeBSD.ORG Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <20010312140636.A18351@fw.wintelcom.net> References: <200103122036.VAA99695@freebsd.dk> <200103122146.f2CLkLs08952@ptavv.es.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <200103122146.f2CLkLs08952@ptavv.es.net>; from oberman@es.net on Mon, Mar 12, 2001 at 01:46:21PM -0800 X-all-your-base: are belong to us. Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG * Kevin Oberman [010312 13:46] wrote: > Soren, > > Thanks for the quick reply! And right on the button, too. > > I have turned the write cache back on (any relevance to "write cache" > being abbreviated to "WC"? :-) and the time to dd the slices went back > to 10 and 5 minutes (actually 489 and 287 seconds). > > How serious is the possible corruption issue, anyway. The loss in > performance is pretty drastic although it may be that dd is an > especially bad case, but I really don't like to corrupt my disks, > either. If basically running with blind write caching turned on is akin to running your filesystem in async mode. This is because write caching gives the drive license to lie about completing a write, the various ordering of writes are effectively bypassed. If you crash without these dependancies actually written to the disk, when you come back up you have a good chance of losing large portions of your filesystem. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] Daemon News Magazine in your snail-mail! http://magazine.daemonnews.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message