From owner-freebsd-fs@FreeBSD.ORG Fri Sep 17 20:09:56 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 77BB6106566C; Fri, 17 Sep 2010 20:09:56 +0000 (UTC) (envelope-from bsdunix44@gmail.com) Received: from mail-yw0-f54.google.com (mail-yw0-f54.google.com [209.85.213.54]) by mx1.freebsd.org (Postfix) with ESMTP id 192228FC0C; Fri, 17 Sep 2010 20:09:55 +0000 (UTC) Received: by ywt2 with SMTP id 2so1063017ywt.13 for ; Fri, 17 Sep 2010 13:09:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:references:in-reply-to :mime-version:content-transfer-encoding:content-type:message-id:cc :x-mailer:from:subject:date:to; bh=qsDznvMWu+D0BTK2jSXhTjOBXcGm/GVWr0BaQEX8N9U=; b=fZgS8816LfVy+ZteGvWwJEc181NPpq1+qevUSJUIg7OGrZgTtfh7k0VeQvbl32ouzy N0OjwqTAFaywLhWy3326SeNYOBrSYjtaL7Tppac01a3LdVtWj3Eh8T9vK/XXJP0ssZXW kzGHkpV9/5TUG73tltU+NFMj29L6qBcbJ7758= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=references:in-reply-to:mime-version:content-transfer-encoding :content-type:message-id:cc:x-mailer:from:subject:date:to; b=aIGfqfn1lSqdouJx+ZrQLt7NFL8HwmoVqnAjGlgkYYPqbvr+TnktkjDQ8ZYvSYFjH6 s1ECEYE14phAmLM+TauaS0YLM0Q4ZEpqYrcnxB6jaI7o3vhWxs2/ZwLb6qRkC1jNlgu7 hU4wrKUjp2s+oqqyQGz4Gi2SPGWn58yYaSsZA= Received: by 10.150.185.18 with SMTP id i18mr5693919ybf.327.1284754193217; Fri, 17 Sep 2010 13:09:53 -0700 (PDT) Received: from [10.1.140.232] (mobile-166-137-142-254.mycingular.net [166.137.142.254]) by mx.google.com with ESMTPS id t16sm5273671ybm.10.2010.09.17.13.09.49 (version=TLSv1/SSLv3 cipher=RC4-MD5); Fri, 17 Sep 2010 13:09:51 -0700 (PDT) References: <82EA2358-F5E5-4CEE-91AC-4211C04F22FD@gmail.com> <20100917193521.GC1902@garage.freebsd.pl> In-Reply-To: <20100917193521.GC1902@garage.freebsd.pl> Mime-Version: 1.0 (iPhone Mail 8B117) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Message-Id: <42855753-ED49-4850-8E9F-DB3DEB984E36@gmail.com> X-Mailer: iPhone Mail (8B117) From: Christopher Watson Date: Fri, 17 Sep 2010 15:10:09 -0500 To: Pawel Jakub Dawidek 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 20:09:56 -0000 I'll be able to test that in 8 hours. Thanks for the reply! I'll post result= s then. Also, what *is* the recommended way to get a more accurate test of f= ile I/O regarding zfs? dd clearly isn't the best tool. Postmark? Blogbench? Chris=20 Sent from my iPhone On Sep 17, 2010, at 2:35 PM, 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 >=20 > 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 > --=20 > Pawel Jakub Dawidek http://www.wheelsystems.com > pjd@FreeBSD.org http://www.FreeBSD.org > FreeBSD committer Am I Evil? Yes, I Am!