From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 1 12:50:16 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 29B611065672 for ; Mon, 1 Jun 2009 12:50:16 +0000 (UTC) (envelope-from tevans.uk@googlemail.com) Received: from mail-ew0-f212.google.com (mail-ew0-f212.google.com [209.85.219.212]) by mx1.freebsd.org (Postfix) with ESMTP id 9FE048FC26 for ; Mon, 1 Jun 2009 12:50:15 +0000 (UTC) (envelope-from tevans.uk@googlemail.com) Received: by ewy8 with SMTP id 8so4322339ewy.43 for ; Mon, 01 Jun 2009 05:50:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:received:received:subject:from:to:cc :in-reply-to:references:content-type:date:message-id:mime-version :x-mailer:content-transfer-encoding; bh=5CGAq8gDYKvy09xYrYiIU7nkkgOCaeBsS25D/kWUMWo=; b=o7J4gCFXqHiIewGulwYzbQCNyIQ+jR9y4Saso9t2uop+LfNaHdVh+MGoIjRSpnUqGt y9hIJMvILmfdkYaLKzo3HfTOzl4j/ORj4lMwtUD4lz9H0o6pGy0JjLDqiNaUl1wM/CF1 rv0TZvB6qfciVhSiBQgx2SoFG74DZ62BWWiDw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=VCvF8AlHyF8qAkg4HfJht0mRUqTAgJw0GUQOafRggPy+MUxGj3speztKkogO7GscHS peGQQmqTuvYFsS4pGgIPoGoDDp35vFfnqaskno5YRZlY4QDk0vrWzVep71fH12SAVGyT LnnIdIh37zA1ZIGAG85hVKplESKF6xWB3yQnQ= Received: by 10.210.13.17 with SMTP id 17mr6378806ebm.59.1243860614639; Mon, 01 Jun 2009 05:50:14 -0700 (PDT) Received: from ?127.0.0.1? (87-194-39-182.bethere.co.uk [87.194.39.182]) by mx.google.com with ESMTPS id 23sm1273810eya.49.2009.06.01.05.50.13 (version=SSLv3 cipher=RC4-MD5); Mon, 01 Jun 2009 05:50:13 -0700 (PDT) From: Tom Evans To: krad In-Reply-To: <3346D963EE2E4D28AE89CB71C2F92939@uk.tiscali.intl> 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> <3346D963EE2E4D28AE89CB71C2F92939@uk.tiscali.intl> Content-Type: text/plain Date: Mon, 01 Jun 2009 13:50:12 +0100 Message-Id: <1243860612.9871.68.camel@strangepork.london.mintel.ad> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1.1 FreeBSD GNOME Team Port Content-Transfer-Encoding: 7bit Cc: freebsd-hackers@freebsd.org, xorquewasp@googlemail.com 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 12:50:16 -0000 On Mon, 2009-06-01 at 09:32 +0100, krad wrote: > Zfs has been designed for highly scalable redundant disk pools therefore > using it on a single drive kind of goes against it ethos. Remember a lot of > the blurb in the man page was written by sun and therefore is written with > corporates in mind, therefore the cost with of the data vs an extra drive > being so large why wouldn't you make it redundant. > > Having said that sata drives are cheap these days so you would have to be on > the tightest of budgets not to do a mirror. > > Having said all this we quite often us zfs on a single drive, well sort of. > The sun clusters have external storage for the shared file systems. These > are usually a bunch of drives, raid 5, 10 or whatever. Then export a single > lun, which is presented to the various nodes. There is a zpool created on > this LUN. So to all intents and purposes zfs thinks its on a single drive > (the redundancy provided by the external array). This is common practice and > we see no issues with it. By doing this surely you lose a lot of the self healing that ZFS offers? For instance, if the underlying vdev is just a raid5, then a disk failure combined with an undetected checksum error on a different disk would lead you to lose all your data. Or am I missing something? (PS, top posting is bad) Tom