From owner-freebsd-questions@FreeBSD.ORG Wed Mar 24 11:33:25 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4635F106564A for ; Wed, 24 Mar 2010 11:33:25 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (gate6.infracaninophile.co.uk [IPv6:2001:8b0:151:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id AD7198FC0A for ; Wed, 24 Mar 2010 11:33:24 +0000 (UTC) Received: from seedling.black-earth.co.uk (seedling.black-earth.co.uk [81.187.76.163]) (authenticated bits=0) by smtp.infracaninophile.co.uk (8.14.4/8.14.4) with ESMTP id o2OBXI0J097838 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Wed, 24 Mar 2010 11:33:19 GMT (envelope-from m.seaman@infracaninophile.co.uk) Message-ID: <4BA9F87E.7050205@infracaninophile.co.uk> Date: Wed, 24 Mar 2010 11:33:18 +0000 From: Matthew Seaman Organization: Infracaninophile User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-GB; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: John References: <20100324103151.GA2598@potato> In-Reply-To: <20100324103151.GA2598@potato> X-Enigmail-Version: 1.0.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Virus-Scanned: clamav-milter 0.95.3 at happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_ADSP_ALL, SPF_FAIL autolearn=no version=3.3.0 X-Spam-Checker-Version: SpamAssassin 3.3.0 (2010-01-18) on happy-idiot-talk.infracaninophile.co.uk Cc: freebsd-questions@freebsd.org Subject: Re: simple zfs query X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Mar 2010 11:33:25 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 24/03/2010 10:31:51, John wrote: > With ZFS and 3x 2Tb SATA disks, what percentage of theoretical diskspace > would I realise? I'm hoping at least 5Tb would be usable? That depends on how you configure your zpool. The choices are: disk -- just uses the disk directly as a vdev. Means you can use 100% of the space, but you have absolutely no resilience mirror -- for which you'ld need an even number of disks and you get 50% of the raw as usable space. Can survive at least one disk failure, and possibly up to as many as half of the disks failing. raidz -- single parity (equivalent to RAID5). For N disks, 1 disk worth is used for parity data, leaving N - 1 disks' worth as the actual capacity. So you'ld get 66% of raw in your case. Can survive failure of any one disk. raidz2 -- double parity (equivalent to RAID6). For N disks, 2 disks worth are used for parity data, leaving N - 2 disks worth as actual capacity. Or 33% of raw in your case. Can survive failure of any two disks. Note that 3 drives is the minimum for either of the raidz types, and won't give you the best performance. See zpool(1M) for details. Cheers, Matthew - -- Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.14 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkup+H4ACgkQ8Mjk52CukIx8HQCfcGTI3wh3QsxNmDS1nPkbw8WU cWIAoJO8rys1R7SfasVkse2htfqOqVrF =AWpE -----END PGP SIGNATURE-----