From owner-freebsd-fs@FreeBSD.ORG Fri Sep 17 20:10:43 2010 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E42861065670 for ; Fri, 17 Sep 2010 20:10:43 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: from mail.garage.freebsd.pl (60.wheelsystems.com [83.12.187.60]) by mx1.freebsd.org (Postfix) with ESMTP id 8D4508FC16 for ; Fri, 17 Sep 2010 20:10:43 +0000 (UTC) Received: by mail.garage.freebsd.pl (Postfix, from userid 65534) id 5B68C45C98; Fri, 17 Sep 2010 22:10:42 +0200 (CEST) Received: from localhost (chello089077043238.chello.pl [89.77.43.238]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.garage.freebsd.pl (Postfix) with ESMTP id 56A0345684; Fri, 17 Sep 2010 22:10:37 +0200 (CEST) Date: Fri, 17 Sep 2010 22:10:21 +0200 From: Pawel Jakub Dawidek To: Chris Watson Message-ID: <20100917201021.GD1902@garage.freebsd.pl> References: <82EA2358-F5E5-4CEE-91AC-4211C04F22FD@gmail.com> <20100917193521.GC1902@garage.freebsd.pl> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="hxkXGo8AKqTJ+9QI" Content-Disposition: inline In-Reply-To: <20100917193521.GC1902@garage.freebsd.pl> User-Agent: Mutt/1.4.2.3i X-PGP-Key-URL: http://people.freebsd.org/~pjd/pjd.asc X-OS: FreeBSD 9.0-CURRENT amd64 X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mail.garage.freebsd.pl X-Spam-Level: X-Spam-Status: No, score=-0.6 required=4.5 tests=BAYES_00,RCVD_IN_SORBS_DUL autolearn=no version=3.0.4 Cc: freebsd-fs@freebsd.org Subject: Re: ZFS I/O Throughput question.. X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 17 Sep 2010 20:10:44 -0000 --hxkXGo8AKqTJ+9QI Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Sep 17, 2010 at 09:35:21PM +0200, Pawel Jakub Dawidek wrote: > On Wed, Sep 15, 2010 at 03:05:46AM -0500, Chris Watson wrote: > > I have been testing ZFS on a home box now for a few days and I have a = =20 > > question that is perplexing me. Everything I have read on ZFS says in = =20 > > almost every case mirroring is faster than raidz. So I initially setup = =20 > > a 2x2 Raid 10 striped mirror. Like so: > [...] >=20 > Could you try running something like this: >=20 > # apply "dd if=3D/dev/ada%1 of=3D/dev/null bs=3D1m count=3D5000 &" 2 3 4= 5 >=20 > This will tell us how much of total throughput do you have. > If you can destroy your data, you may also try this: >=20 > # apply "dd if=3D/dev/null of=3D/dev/ada%1 bs=3D1m count=3D5000 &" 2 3 4= 5 # apply "dd if=3D/dev/zero of=3D/dev/ada%1 bs=3D1m count=3D5000 &" 2 3 4 5 Thanks to se@ for noticing this. > If you disks cannot work at full speed in parallel this might explain > what you're seeing. Mirror send to disk twice as much data as it > receives and RAIDZ sends only 33% more data in four disk case. >=20 > And no, there are neither special RAIDZ optimizations not special mirror > pesimizations in FreeBSD. --=20 Pawel Jakub Dawidek http://www.wheelsystems.com pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --hxkXGo8AKqTJ+9QI Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iEYEARECAAYFAkyTyywACgkQForvXbEpPzQNuwCfbYa9OSUjAQQDIfLY2RBnVh9E y2kAn3DdRqbA6PTH3qRYHwe1LoA5WqSy =jbFu -----END PGP SIGNATURE----- --hxkXGo8AKqTJ+9QI--