From owner-freebsd-fs@FreeBSD.ORG Sat Sep 20 09:31:17 2008 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 3C2861065679 for ; Sat, 20 Sep 2008 09:31:17 +0000 (UTC) (envelope-from andrew@modulus.org) Received: from email.octopus.com.au (host-122-100-2-232.octopus.com.au [122.100.2.232]) by mx1.freebsd.org (Postfix) with ESMTP id EF2BE8FC1B for ; Sat, 20 Sep 2008 09:31:11 +0000 (UTC) (envelope-from andrew@modulus.org) Received: by email.octopus.com.au (Postfix, from userid 1002) id 51E0B17369; Sat, 20 Sep 2008 19:31:09 +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] (142.19.96.58.exetel.com.au [58.96.19.142]) (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 C5DE317261 for ; Sat, 20 Sep 2008 19:31:04 +1000 (EST) Message-ID: <48D4C2AA.8080000@modulus.org> Date: Sat, 20 Sep 2008 19:30:18 +1000 From: Andrew Snow User-Agent: Thunderbird 2.0.0.14 (X11/20080523) MIME-Version: 1.0 To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: zfs benchmarks and 7 disk raidz oddity 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: Sat, 20 Sep 2008 09:31:17 -0000 Hi all, I am running 8-CURRENT with ZFS patches on a 3ghz Core2Duo with Intel P45 chipset. I took some benchmarks of ZFS on six old SATA disks and one PATA, onboard controllers only, and I expect you are interested to see the results. The disks range in size from 200gb to 320gb. I tried several configurations with quick and dirty testing. Listed below is the sequential megabytes/sec rating as measured by dd bs=1m for a 10GB file. All ZFS settings were left at their defaults. Conf Write Read (MB/s) ------------------------------------ 7 disk RAIDZ2 220 305 7 disk RAIDZ1 84 361 7 disk striped 318 409 7 disk stripe copies=2 140 164 6 disk RAIDZ2 173 260 6 disk RAIDZ1 238 307 6 disk striped 280 346 6 disk 2xRAIDZ1 striped 188 251 6 disk striped mirrors 164 323 6 disk stripe copies=2 151 179 A few notes: 1. using copies=2 is a nice way to be able to get RAID1-like mirroring reliability but on an odd number of disks. However you take a noticeable performance penalty: Write speed is fine but read speed is almost half of what RAID0+1 achieved. 2. RAIDZ1 and RAIDZ2 are fast and efficient. However in total it caused the system to use almost all of one CPU core during writing. 3. There seemed to be a bug with 7 disks and RAIDZ1 - the write performance was terrible! When I ran "gstat" I noticed it was spending much time writing to only two disks most of the time, which became a serious bottleneck - the worst write score of the lot. Read was fine. Perhaps the algorithm isn't optimised for choosing parity locations out of exactly 7 disks? - Andrew