From owner-freebsd-stable@FreeBSD.ORG Sat Aug 18 08:11:22 2007 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2FD2816A419 for ; Sat, 18 Aug 2007 08:11:22 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (ns0.infracaninophile.co.uk [IPv6:2001:8b0:151:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id 923F513C45B for ; Sat, 18 Aug 2007 08:11:21 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from happy-idiot-talk.infracaninophile.co.uk (localhost.infracaninophile.co.uk [IPv6:::1]) by smtp.infracaninophile.co.uk (8.14.1/8.14.1) with ESMTP id l7I8BEnK052963; Sat, 18 Aug 2007 09:11:16 +0100 (BST) (envelope-from m.seaman@infracaninophile.co.uk) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=infracaninophile.co.uk; s=200708; t=1187424676; bh=dNF4gmPez72dlo 1ONkiwhZ5ROJHrHCNn7uBOgYUBF8U=; h=Message-ID:Date:From:Organization: User-Agent:MIME-Version:To:CC:Subject:References:In-Reply-To: X-Enigmail-Version:Content-Type:Content-Transfer-Encoding:Cc: Content-Type:Date:From:In-Reply-To:Message-ID:Mime-Version: References:To; b=AqN9M6hX8u7XbIzWuDN/ph1EDiRaX140iPMTZJGWmL9Xdk0NG eBIrnlEiKfr2sX+Qk3kqiu42Ue8LsNdk2hAFVFlVmDbOp7kWnSsv3nLXdmLvPbZQkD5 Mdye0I00+x0EHiCgRLHgx9CVGHYoC+oqTWppE0hRWHEv5nbnO/04ebA= Message-ID: <46C6A9A2.70209@infracaninophile.co.uk> Date: Sat, 18 Aug 2007 09:11:14 +0100 From: Matthew Seaman Organization: Infracaninophile User-Agent: Thunderbird 2.0.0.6 (X11/20070803) MIME-Version: 1.0 To: Clayton Milos References: <31BB09D7-B58A-47AC-8DD1-6BB8141170D8@khera.org> <000f01c7e122$1d91a390$0301a8c0@claylaptop> In-Reply-To: <000f01c7e122$1d91a390$0301a8c0@claylaptop> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (smtp.infracaninophile.co.uk [IPv6:::1]); Sat, 18 Aug 2007 09:11:16 +0100 (BST) X-Virus-Scanned: ClamAV 0.91.1/3980/Sat Aug 18 06:58:54 2007 on happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-2.8 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VERIFIED,NO_RELAYS,SUBJECT_FUZZY_TION autolearn=no version=3.2.3 X-Spam-Checker-Version: SpamAssassin 3.2.3 (2007-08-08) on happy-idiot-talk.infracaninophile.co.uk Cc: Vivek Khera , FreeBSD Stable Subject: Re: large RAID volume partition strategy X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 18 Aug 2007 08:11:22 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Clayton Milos wrote: > If you want awesome performance and reliability the real way to go is > RAID10 (or more correctly RAID 0+1). RAID10 and RAID0+1 are very different beasts. RAID10 is the best choice for a read/write intensive f/s with valuable data, exactly what you need to support a RDBMS. It is built by pairing up all of the drives as RAID1 mirrors[*] and then creating a RAID0 stripe across all of the mirrors. It's the least economical RAID setup, giving you a usable space which is 50% of the total raw disk space, but it is the most resilient -- potentially being able to survive half of the drives failing -- and much the best performing of the RAID types. RAID0+1 on the other hand is what you give to someone you don't like very much. In this case, you divide the disks into two equal sets, create a RAID0 stripe over each set and then a RAID1 mirror over the stripes. It has the /delightful/ feature that failure of any one drive immediately puts half of the available disks out of action: ie it is *less* resilient than any other RAID setup (other than a RAID0 stripe over all the drives). Space economy-wise it's exactly like RAID10 and performance characteristics are pretty similar to RAID10, leading to the obvious conclusion: use RAID10 instead. Cheers, Matthew [*] The correctly paranoid sysadmin will of course ensure that each of the disks in those pairs hangs off a different bus, comes from a different manufacturing batch and is preferably connected to a different controller and with different, independent power supplies. Or, in extreme cases, that each half of the mirrors are in completely different datacenters. - -- 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 v2.0.4 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGxqmh8Mjk52CukIwRCPvyAJ4k/POTK9Moqu80nV9TKHZqLIC5ngCfYEd4 oiV2MAAiFIXcNSTSiCM4D6M= =GDZN -----END PGP SIGNATURE-----