From owner-freebsd-fs@FreeBSD.ORG Thu Jul 19 19:34:04 2007 Return-Path: X-Original-To: freebsd-fs@freebsd.org Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 0BD9716A403 for ; Thu, 19 Jul 2007 19:34:04 +0000 (UTC) (envelope-from M.S.Powell@salford.ac.uk) Received: from abbe.salford.ac.uk (abbe.salford.ac.uk [146.87.0.10]) by mx1.freebsd.org (Postfix) with SMTP id 8266113C428 for ; Thu, 19 Jul 2007 19:34:02 +0000 (UTC) (envelope-from M.S.Powell@salford.ac.uk) Received: (qmail 18975 invoked by uid 98); 19 Jul 2007 20:34:01 +0100 Received: from 146.87.255.121 by abbe.salford.ac.uk (envelope-from , uid 401) with qmail-scanner-2.01 (clamdscan: 0.90/3700. spamassassin: 3.1.8. Clear:RC:1(146.87.255.121):. Processed in 0.056676 secs); 19 Jul 2007 19:34:01 -0000 Received: from rust.salford.ac.uk (HELO rust.salford.ac.uk) (146.87.255.121) by abbe.salford.ac.uk (qpsmtpd/0.3x.614) with SMTP; Thu, 19 Jul 2007 20:34:01 +0100 Received: (qmail 5853 invoked by uid 1002); 19 Jul 2007 19:33:59 -0000 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 19 Jul 2007 19:33:59 -0000 Date: Thu, 19 Jul 2007 20:33:59 +0100 (BST) From: "Mark Powell" To: Doug Rabson In-Reply-To: <200707192027.44025.dfr@rabson.org> Message-ID: <20070719203134.B4923@rust.salford.ac.uk> References: <20070719102302.R1534@rust.salford.ac.uk> <20070719135510.GE1194@garage.freebsd.pl> <20070719181313.G4923@rust.salford.ac.uk> <200707192027.44025.dfr@rabson.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-fs@freebsd.org Subject: Re: ZfS & GEOM with many odd drive sizes 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: Thu, 19 Jul 2007 19:34:04 -0000 On Thu, 19 Jul 2007, Doug Rabson wrote: > On Thursday 19 July 2007, Mark Powell wrote: >> Should I expect much greater CPU usage with ZFS? >> I previously had a geom raid5 array which barely broke a sweat on >> benchmarks i.e simple large dd read and writes. With ZFS on the same >> hardware I notice 50-60% system CPU usage is usual during such tests. >> Before the network was a bottleneck, but now it's the zfs array. I >> expected it would have to do a bit more 'thinking', but is such a >> dramatic increase normal? >> >> Many thanks again. > > ZFS does a checksum on every block it reads from the disk which may be > your problem. In normal usage, this isn't a big deal due because many > reads get data from the cache. I've turned off checksums, but still my machine is struggling. I think my Athlon XP is a little old for all this work :( Any other tips for speeding zfs up? Cheers. -- Mark Powell - UNIX System Administrator - The University of Salford Information Services Division, Clifford Whitworth Building, Salford University, Manchester, M5 4WT, UK. Tel: +44 161 295 4837 Fax: +44 161 295 5888 www.pgp.com for PGP key