From owner-freebsd-stable@FreeBSD.ORG Thu Jul 9 23:13:36 2009 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 78CFD106566C for ; Thu, 9 Jul 2009 23:13:36 +0000 (UTC) (envelope-from andrew@modulus.org) Received: from email.octopus.com.au (email.octopus.com.au [122.100.2.232]) by mx1.freebsd.org (Postfix) with ESMTP id 37B8A8FC13 for ; Thu, 9 Jul 2009 23:13:35 +0000 (UTC) (envelope-from andrew@modulus.org) Received: by email.octopus.com.au (Postfix, from userid 1002) id 8328117DAE; Fri, 10 Jul 2009 09:14:00 +1000 (EST) X-Spam-Checker-Version: SpamAssassin 3.2.3 (2007-08-08) on email.octopus.com.au X-Spam-Level: X-Spam-Status: No, score=-1.4 required=10.0 tests=ALL_TRUSTED autolearn=failed version=3.2.3 Received: from [10.1.50.60] (ppp121-44-41-14.lns10.syd7.internode.on.net [121.44.41.14]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: admin@email.octopus.com.au) by email.octopus.com.au (Postfix) with ESMTP id 7AC5E1736A; Fri, 10 Jul 2009 09:13:56 +1000 (EST) Message-ID: <4A567919.8000704@modulus.org> Date: Fri, 10 Jul 2009 09:11:21 +1000 From: Andrew Snow User-Agent: Thunderbird 2.0.0.14 (X11/20080523) MIME-Version: 1.0 To: "Patrick M. Hausen" References: <20090709112512.GA44158@hugo10.ka.punkt.de> <73a41d4b72d62b0bfe3d0fb7206376a8.squirrel@cygnus.homeunix.com> <20090709123434.GC46563@hugo10.ka.punkt.de> <4A55EEEC.3030007@interazioni.it> <20090709134302.GA50485@hugo10.ka.punkt.de> In-Reply-To: <20090709134302.GA50485@hugo10.ka.punkt.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-stable@freebsd.org, "Tonix \(Antonio Nati\)" Subject: Re: ZFS - thanks 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: Thu, 09 Jul 2009 23:13:36 -0000 Patrick M. Hausen wrote: > You cannot escape the poor write performance of RAID 5 and > comparable setups with or without hardware. No matter how > much you cache, one time a block must be written to disk. ZFS RAIDZ works differently: It is based on variable-sized blocks written to the disks based on incoming data stream, grouped into transactions. This makes it very efficient for clustering multi-threaded random I/O writes together into large physical disk writes. (The downside is it has to read the entire "stripe" even if you are only reading one byte, in order to calculate and verify the checksum.) - Andrew