From owner-freebsd-stable@FreeBSD.ORG Wed Oct 25 13:50:13 2006 Return-Path: X-Original-To: freebsd-stable@FreeBSD.ORG Delivered-To: freebsd-stable@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C675516A407 for ; Wed, 25 Oct 2006 13:50:13 +0000 (UTC) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (lurza.secnetix.de [83.120.8.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id A787443D46 for ; Wed, 25 Oct 2006 13:50:12 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (qlwxkl@localhost [127.0.0.1]) by lurza.secnetix.de (8.13.4/8.13.4) with ESMTP id k9PDo4Cp086251; Wed, 25 Oct 2006 15:50:10 +0200 (CEST) (envelope-from oliver.fromme@secnetix.de) Received: (from olli@localhost) by lurza.secnetix.de (8.13.4/8.13.1/Submit) id k9PDo442086250; Wed, 25 Oct 2006 15:50:04 +0200 (CEST) (envelope-from olli) Date: Wed, 25 Oct 2006 15:50:04 +0200 (CEST) Message-Id: <200610251350.k9PDo442086250@lurza.secnetix.de> From: Oliver Fromme To: freebsd-stable@FreeBSD.ORG, guido@gvr.org In-Reply-To: <20061025132455.GA52157@gvr.gvr.org> X-Newsgroups: list.freebsd-stable User-Agent: tin/1.8.2-20060425 ("Shillay") (UNIX) (FreeBSD/4.11-STABLE (i386)) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.1.2 (lurza.secnetix.de [127.0.0.1]); Wed, 25 Oct 2006 15:50:10 +0200 (CEST) Cc: Subject: Re: Gmirror performanc X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Oct 2006 13:50:13 -0000 Guido van Rooij wrote: > Anyway, I created a gm device and a partition. Now the read performance > is not what I'd expect. > I have the partition on two SATA devices on different controlers. > I get around 60MB/s for each disk. I can get that speed from both disks > simultaneously. > Now when I dd from the gm device, I don't get any speed higher than that. That's expected. > I tried with -b split -s , -b round-robin, -b load. > (dd-ing as done with a bs of 1m; I see the transaction size is 128Kb, > unless the split method is used, in which case the transaction size > gies down. When round-robin is used, the transaction size is 128Kb/s, > but the number of transaction per second goes down.). > > I cannot explain why I should not get a higher read speed. Anyone? dd is a sequential, single-threaded operation, so it will only use one disk at a time. It's not really suitable as a benchmark for real-world things. In the real world [TM] you have multiple processes that access the file system at random. Here you will benefit from the mirror, because accesses will be distributed among the disks. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "anyone new to programming should be kept as far from C++ as possible; actually showing the stuff should be considered a criminal offence" -- Jacek Generowicz