From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 1 00:15:51 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BEA65106564A for ; Mon, 1 Jun 2009 00:15:51 +0000 (UTC) (envelope-from mwm-keyword-freebsdhackers2.e313df@mired.org) Received: from mired.org (two.mired.org [74.143.213.43]) by mx1.freebsd.org (Postfix) with ESMTP id 66B348FC08 for ; Mon, 1 Jun 2009 00:15:51 +0000 (UTC) (envelope-from mwm-keyword-freebsdhackers2.e313df@mired.org) Received: (qmail 13459 invoked by uid 1001); 31 May 2009 20:14:09 -0400 Received: from bhuda.mired.org (localhost.localdomain [127.0.0.1]) by bhuda (tmda-ofmipd) with ESMTP; Sun, 31 May 2009 20:14:09 -0400 Date: Sun, 31 May 2009 20:14:08 -0400 To: xorquewasp@googlemail.com Message-ID: <20090531201408.45dd4334@bhuda.mired.org> In-Reply-To: <20090531235943.GA77374@logik.internal.network> References: <20090530175239.GA25604@logik.internal.network> <20090530144354.2255f722@bhuda.mired.org> <20090530191840.GA68514@logik.internal.network> <20090530162744.5d77e9d1@bhuda.mired.org> <20090531201445.GA82420@logik.internal.network> <0229B3BF1BE94C82AA11FD06CBE0BDEF@uk.tiscali.intl> <20090531235943.GA77374@logik.internal.network> Organization: Meyer Consulting X-Mailer: Claws Mail 3.7.1 (GTK+ 2.14.7; amd64-portbld-freebsd7.1) Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwBAMAAAClLOS0AAAAG1BMVEXguIzRkGnhyaz069mXhW0WHRnbrnR9WCQ6LB0CchNMAAACSUlEQVQ4jV2TQW7jMAxFGaPQOgQEdZaGMsgBrAvUA03dCxj1Uu4U2gfwQD7AGNax51NK07RcxXz6/CSl0Ij450vkPG1jzpIZM1UwDCl/xB14TWnNX8A00Qj5a0mnVFVbVUz4MeErea2HikSRqZzY894zwg9p2+/AtO8LzxFED+tNAUFeU29iFOLRxlZAcdo9A8wi8ZBMV4BKPde82Oxrvs6BTkulQIClte0DLFzzsKk9j1MBex8iUaP00Bd78S/muyFScrTXz6zLkEUxJp+SabQfNOs4f4Jpx5qSZ/304PWwlEWP1cOn/mJQR7EOD+uKhjcBLziuL7xoY5Xm+VFAUSw/LwwwsHEHxihpwV4EJH0xXRkbw1PkRw+X4pEuSJwBggqk+HEYKkiL5/74/nQkogigzQsAFrakxZyfw3wMIEEZPv4AWMfxwqE5GNxGaERjmH+PG8AE0L4/w9g0lsp1raLYAN5azQa+AOoO9NwcpFkTrG2VKNMNEL5UKUUAw34tha0z7onUG0oBoNtczE04GwFE3wCHc0ChezAJ6A1WMV81AtY7wDAJSlXwV+4cwBvsOsrQMRawfQEBz0deEZ7WNpV2szckIKo5VpDHDSDvF1GItwqqAlG01Hh50BGtVhuUkjkasg/14bYFGCgWg1fSWHvmOoJck2xdp9ZvZBHzDVTzX23TkrOn7qe5U2COEw5D4Vx3qEQpFY2Z/3QFnJxzp7YCmSMG19nOUoe869zZfOQb5ywQuWu0yCn5+8gxZz+BE7vG3j4/wbf4D/sXN9Wug1s7AAAAAElFTkSuQmCC Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Delivery-Agent: TMDA/1.1.12 (Macallan) From: Mike Meyer Cc: freebsd-hackers@freebsd.org Subject: Re: Request for opinions - gvinum or ccd? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Jun 2009 00:15:52 -0000 On Mon, 1 Jun 2009 00:59:43 +0100 xorquewasp@googlemail.com wrote: > There is one last thing I'd like clarified. From the zpool > manpage: > > In order to take advantage of these features, a pool must make use of > some form of redundancy, using either mirrored or raidz groups. While > ZFS supports running in a non-redundant configuration, where each root > vdev is simply a disk or file, this is strongly discouraged. A single > case of bit corruption can render some or all of your data unavailable. > > Is this supposed to mean: > > "ZFS is more fragile than most. If you don't use redundancy, one > case of bit corruption will destroy the filesystem" > > Or: > > "Hard disks explode often. Use redundancy." How about (from an old disk recover paper): Disks, unlike software, sometimes fail. Using redundancy can help you prevent this from resulting in data loss. That said, there aren't many file systems that can recover from data errors in the underlying storage. ZFS appropriately configured is one. I don't believe the default config is appropriate, though. You need both checksum on and copies > 1 on, and the latter isn't the default. It's probably better to let zpool provide the redundancy via a mirror or raid configuration than to let zfs do it anyway. http://www.mired.org/consulting.html Independent Network/Unix/Perforce consultant, email for more information. O< ascii ribbon campaign - stop html mail - www.asciiribbon.org