From owner-freebsd-fs@FreeBSD.ORG Thu Jul 19 19:47:37 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 8BD6016A402 for ; Thu, 19 Jul 2007 19:47:37 +0000 (UTC) (envelope-from dfr@rabson.org) Received: from itchy.rabson.org (mailgate.nlsystems.com [80.177.232.242]) by mx1.freebsd.org (Postfix) with ESMTP id 228BA13C481 for ; Thu, 19 Jul 2007 19:47:36 +0000 (UTC) (envelope-from dfr@rabson.org) Received: from herring.rabson.org (herring.rabson.org [80.177.232.250]) by itchy.rabson.org (8.13.3/8.13.3) with ESMTP id l6JJlZa5053810; Thu, 19 Jul 2007 20:47:35 +0100 (BST) (envelope-from dfr@rabson.org) From: Doug Rabson To: "Mark Powell" Date: Thu, 19 Jul 2007 20:47:34 +0100 User-Agent: KMail/1.9.6 References: <20070719102302.R1534@rust.salford.ac.uk> <200707192027.44025.dfr@rabson.org> <20070719203134.B4923@rust.salford.ac.uk> (sfid-20070719_20342_28B5762E) In-Reply-To: <20070719203134.B4923@rust.salford.ac.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707192047.34979.dfr@rabson.org> X-Virus-Scanned: ClamAV 0.87.1/3700/Thu Jul 19 14:13:47 2007 on itchy.rabson.org X-Virus-Status: Clean Cc: freebsd-fs@freebsd.org Subject: Re: UNS: 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 19:47:37 -0000 On Thursday 19 July 2007, Mark Powell wrote: > 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. Nothing really comes to mind. You could try simpler geometries (e.g. mirrors or collections of mirrors). Having at least some of your drives in a simple configuration might be useful - I'm working on ZFS boot code at the moment and I don't intend to support raidz or raidz2 (at least to start with). Collections of mirrors and simple disks are much easier.