From owner-freebsd-questions@FreeBSD.ORG Wed Aug 6 02:23:45 2014 Return-Path: <owner-freebsd-questions@FreeBSD.ORG> Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id E784065E for <freebsd-questions@freebsd.org>; Wed, 6 Aug 2014 02:23:44 +0000 (UTC) Received: from na01-bn1-obe.outbound.protection.outlook.com (mail-bn1blp0186.outbound.protection.outlook.com [207.46.163.186]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mail.protection.outlook.com", Issuer "MSIT Machine Auth CA 2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 8B69F2AFC for <freebsd-questions@freebsd.org>; Wed, 6 Aug 2014 02:23:43 +0000 (UTC) Received: from [IPv6:2601:2:4780:2fd:e806:9aa:f68a:db81] (2601:2:4780:2fd:e806:9aa:f68a:db81) by BY1PR0301MB0840.namprd03.prod.outlook.com (25.160.193.146) with Microsoft SMTP Server (TLS) id 15.0.995.14; Wed, 6 Aug 2014 02:23:34 +0000 Message-ID: <53E191A1.6010603@my.hennepintech.edu> Date: Tue, 5 Aug 2014 21:23:29 -0500 From: Andrew Berg <aberg010@my.hennepintech.edu> User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: <freebsd-questions@freebsd.org> Subject: Re: ZFS under FreeBSD failure modes References: <53DAFCF2.2070909@hiwaay.net> <alpine.BSF.2.11.1407312131550.50731@wonkity.com> <53DB9797.1010702@hiwaay.net> <20140801164335.GA16376@slackbox.erewhon.home> <53DBF71D.3080807@hiwaay.net> <20140801232843.GB17393@slackbox.erewhon.home> <53DCF32A.30700@hiwaay.net> <20140802185442.GA28910@slackbox.erewhon.home> <53DD533D.7090700@hiwaay.net> <alpine.BSF.2.11.1408021524130.36114@wonkity.com> <20140802213848.GC77128@neutralgood.org> <BDD126F3-3DF2-4A96-A3CD-9C2C8CE220FE@kraus-haus.org> In-Reply-To: <BDD126F3-3DF2-4A96-A3CD-9C2C8CE220FE@kraus-haus.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [2601:2:4780:2fd:e806:9aa:f68a:db81] X-ClientProxiedBy: BN3PR0301CA0018.namprd03.prod.outlook.com (25.160.180.156) To BY1PR0301MB0840.namprd03.prod.outlook.com (25.160.193.146) X-Microsoft-Antispam: BCL:0;PCL:0;RULEID: X-Forefront-PRVS: 02951C14DC X-Forefront-Antispam-Report: SFV:NSPM; SFS:(6009001)(199002)(51704005)(24454002)(189002)(54356999)(110136001)(89122001)(92566001)(50986999)(77096002)(87266999)(99396002)(50466002)(76176999)(107886001)(93886004)(74502001)(74662001)(2351001)(107046002)(65816999)(92726001)(85306004)(64706001)(101416001)(76482001)(83506001)(79102001)(59896001)(77982001)(81542001)(20776003)(81342001)(105586002)(33656002)(47776003)(19580395003)(19580405001)(86362001)(42186005)(23676002)(80316001)(102836001)(87976001)(83322001)(83072002)(4396001)(31966008)(75432001)(88552001)(46102001)(85852003)(21056001)(65956001)(65806001)(106356001)(95666004)(80022001)(3826002); DIR:OUT; SFP:; SCL:1; SRVR:BY1PR0301MB0840; H:[IPv6:2601:2:4780:2fd:e806:9aa:f68a:db81]; FPR:; MLV:sfv; PTR:InfoNoRecords; MX:1; LANG:en; X-OriginatorOrg: my.hennepintech.edu X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: User questions <freebsd-questions.freebsd.org> List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-questions>, <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe> List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions/> List-Post: <mailto:freebsd-questions@freebsd.org> List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help> List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, <mailto:freebsd-questions-request@freebsd.org?subject=subscribe> X-List-Received-Date: Wed, 06 Aug 2014 02:23:45 -0000 On 2014.08.05 20:19, Paul Kraus wrote: > On Aug 2, 2014, at 17:38, kpneal@pobox.com wrote: > >> I'd be careful running ZFS on a machine that lacks ECC memory. Lots of >> people do it, but I'd be worried that ZFS would get itself into a state >> where you couldn't access anything. > > I am startring to see comments like this on a more frequent basis. What is the failure mechanism you expect to run into here? The idea is that a bad block in RAM will get written to disk and ZFS will not know it is bad and then create a checksum based on it and call it good. However, UFS and other filesystems would be just as incapable of detecting and correcting the error. Yes, ECC RAM is always better than non-ECC RAM, but ZFS is still going to be better equipped to detect errors than UFS. Not having ECC RAM is more reason to use ZFS, not less. >> When was the last time anyone heard of a UFS file >> system being so damaged that it couldn't be recovered? > > Anecdotal evidence at best. I have plenty of anecdotal evidence that ZFS never looses data. I don’t claim it as fact. The thing to remember is that ZFS is far more capable of finding data corruption than UFS and it will complain loudly whether it can correct the situation or not. To the person unfamiliar with ZFS, this can make it seem like ZFS causes more problems when in fact ZFS is just finding problems that were already there that another filesystem would miss.