From owner-freebsd-stable@FreeBSD.ORG Mon Aug 29 19:32:47 2005 Return-Path: X-Original-To: freebsd-stable@freebsd.org 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 B22CE16A41F; Mon, 29 Aug 2005 19:32:47 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id 47AC143D45; Mon, 29 Aug 2005 19:32:47 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id 845FD5F62; Mon, 29 Aug 2005 15:32:46 -0400 (EDT) Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 08337-09; Mon, 29 Aug 2005 15:32:45 -0400 (EDT) Received: from [192.168.1.3] (pool-68-161-79-217.ny325.east.verizon.net [68.161.79.217]) by pi.codefab.com (Postfix) with ESMTP id 8943F5F4C; Mon, 29 Aug 2005 15:32:44 -0400 (EDT) Message-ID: <431362ED.9030800@mac.com> Date: Mon, 29 Aug 2005 15:33:01 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.11) Gecko/20050801 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Matthias Buelow References: <20050829120415.GA1462@drjekyll.mkbuelow.net> <200508291836.j7TIaVEk013147@gw.catspoiler.org> <20050829185933.GB1462@drjekyll.mkbuelow.net> In-Reply-To: <20050829185933.GB1462@drjekyll.mkbuelow.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: amavisd-new at codefab.com Cc: Don Lewis , freebsd-stable@freebsd.org Subject: Re: Sysinstall automatic filesystem size generation. X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 29 Aug 2005 19:32:47 -0000 Matthias Buelow wrote: > Don Lewis wrote: [ ... ] >> Did you remember to disable write caching by setting the WCE mode page >> bit to zero? At least with SCSI, it doesn't seem to affect performance >> under most workloads. > > No.. I thought that with SCSI it is "ok" to leave the cache enabled > because SCSI supports some sort of request queueing which doesn't > break the order established by softupdates? That gives you the ability to sequence events, yes, but it doesn't mean that data which has been cached by the drive and not yet written out is fine if the power goes away. Good SCSI/RAID controllers have a small battery backup inside the computer case to address exactly this: aac0: mem 0xf0000000-0xf7ffffff irq 31 at device 2.1 on pci2 aac0: i960RX 100MHz, 118MB cache memory, optional battery present aac0: Kernel 2.5-0, Build 2991, S/N xxxxx That cache will get flushed to disk even if the OS goes bonkers or disappears entirely due to no power. Maybe something like this would make you happier: # cat >> /etc/sysctl.conf kern.filedelay=7 kern.dirdelay=6 kern.metadelay=5 ...? >> Softupdates only tries to guarantee that the on-disk file system is in a >> consistent state at all times, with the possible exception that not all >> space may be accounted for. > > It doesn't try very hard, though, nor is it very successful. Look, there is a tradeoff between price/performance/quality (or reliability) in most circumstances. If you want more reliability, pay more to get good hardware, or accept that there will be performance loss if/when you choose to maximize reliability. It's also true that FreeBSD could do a better job or otherwise be improved. You don't have to argue that point, we're already convinced. Submitting improvements is useful. Would changing the sysctls above to shorter defaults be a good idea? -- -Chuck PS: Haven't we had this conversation before?