From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (unknown [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id 4646D1381FA for ; Wed, 28 May 2014 16:10:19 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 52708E0874; Wed, 28 May 2014 16:10:17 +0000 (UTC) Received: from mail-ve0-f171.google.com (mail-ve0-f171.google.com [209.85.128.171]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 589ACE0841 for ; Wed, 28 May 2014 16:10:16 +0000 (UTC) Received: by mail-ve0-f171.google.com with SMTP id oz11so12637935veb.2 for ; Wed, 28 May 2014 09:10:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:content-type; bh=go3eE1jal3xMaazfmhuh43f9xA1SD9z4pvbygH0cF8c=; b=dJgYN20yuhajaQ5lA6LrezAST175VSR4SsDcUhnhTugv5dNxZBCitG8VMEpQCoCVgU DFToXIhTdpRwiuoX5diVcmOKakbP8ow9/6wGQtAw1bi04iRBk5kjyPjTPV3Kj+b5PAfB jZIMD1xm7cL3lcet8bA76mek13J3JQO60ahvt+cQjIquV6uY/ueRCjmH1i6GL5t2YTs5 ldi2A4JhgDbdC9kJZeC8GyhA63ONSeF0a5RAplSOpTO6+8YAAoTSJUduNi/V6Y2R4HZb l9gzlnflehG8FvD2dqMQ9qlwqhjx/ZQjJP9ixVYk9N/0OJEZtuXeEcolI+ZnkU5jN3oE x1OQ== Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-amd64@lists.gentoo.org Reply-to: gentoo-amd64@lists.gentoo.org MIME-Version: 1.0 X-Received: by 10.220.98.143 with SMTP id q15mr841396vcn.38.1401293415519; Wed, 28 May 2014 09:10:15 -0700 (PDT) Sender: freemanrich@gmail.com Received: by 10.52.30.227 with HTTP; Wed, 28 May 2014 09:10:15 -0700 (PDT) In-Reply-To: <20140528152658.GA13493@sgi.com> References: <20140527223938.GA3701@sgi.com> <20140528015114.3634f6b4@marcec> <20140528152658.GA13493@sgi.com> Date: Wed, 28 May 2014 12:10:15 -0400 X-Google-Sender-Auth: tiUyvh5Lwvwy-taedFESbDgyUIc Message-ID: Subject: Re: [gentoo-amd64] Soliciting new RAID ideas From: Rich Freeman To: gentoo-amd64@lists.gentoo.org Content-Type: text/plain; charset=UTF-8 X-Archives-Salt: e5f9f45b-485d-4926-ba0a-7f680710f2bf X-Archives-Hash: dd179a12618801520cea2542c619f3ad On Wed, May 28, 2014 at 11:26 AM, Bob Sanders wrote: > Marc Joliet, mused, then expounded: >> Am Tue, 27 May 2014 15:39:38 -0700 >> schrieb Bob Sanders : >> >> While I am far from a filesystem/storage expert (I see myself as a mere user), >> the cited threads lead me to believe that this is most likely an >> overhyped/misunderstood class of errors (e.g., posts [1] and [2]), so I would >> suggest reading them in their entirety. >> >> [0] http://comments.gmane.org/gmane.comp.file-systems.btrfs/31832 >> [1] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/31871 >> [2] http://permalink.gmane.org/gmane.comp.file-systems.btrfs/31877 >> [3] http://comments.gmane.org/gmane.comp.file-systems.btrfs/31821 >> > > FWIW - here's the FreeNAS ZFS ECC discussion on what happens with a bad > memory bit and no ECC memory: > > http://forums.freenas.org/index.php?threads/ecc-vs-non-ecc-ram-and-zfs.15449/ > I don't think that anybody debates that if you use btrfs/zfs with non-ECC RAM you can potentially lose some of the protection afforded by the checksumming. What I'd question is that this is some concern unique to btrfs/zfs. I'd think the same failure modes would all apply to any other filesystem. So, the message should be that ECC RAM is better than non-ECC RAM, not that those who use non-ECC RAM are better off using ext4 instead of zfs/btrfs. I'd think that any RAM-related issue that would impact zfs/btrfs would affect ext4 just as badly, and with ext4 you're also vulnerable to all the non-RAM-related errors that checksumming was created to solve. If your RAM is bad then all kinds of stuff can go wrong. Ditto for your cache memory in the CPU, logic circuitry in the CPU, your busses, etc. Most systems are not fault-tolerant of these system components and the cost to make them fault-tolerant tends to be fairly high. On the other hand, the good news is that you're far more likely to have problems with data stored on a disk than in RAM, which is probably why we haven't bothered to improve the other components. Rich