From owner-freebsd-stable@FreeBSD.ORG Tue Apr 22 06:02:07 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5F98A106566C for ; Tue, 22 Apr 2008 06:02:07 +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 22A698FC13 for ; Tue, 22 Apr 2008 06:02:06 +0000 (UTC) (envelope-from andrew@modulus.org) Received: by email.octopus.com.au (Postfix, from userid 1002) id 3EBAD13FA3; Tue, 22 Apr 2008 16:02:05 +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 anzac.hos (132.169.233.220.exetel.com.au [220.233.169.132]) (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 2E86E13ABF; Tue, 22 Apr 2008 16:02:01 +1000 (EST) Message-ID: <480D7F58.1080203@modulus.org> Date: Tue, 22 Apr 2008 16:02:00 +1000 From: Andrew Snow User-Agent: Thunderbird 2.0.0.0 (X11/20070426) MIME-Version: 1.0 To: Pete French , freebsd-stable@freebsd.org References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Subject: Re: Dreadful gmirror performance, though each half works fine 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: Tue, 22 Apr 2008 06:02:07 -0000 Pete French wrote: > I did some benchmarking, and "load" gives me a bit better performance than > "round-robin" so I've elected to use that. Haven't tried "prefer" as > syncing all the drives backwards and forwards to get the preferences set > seems a bit too much like hard work! I use this patch for sbin/geom/class/mirror/geom_mirror.c Change: md.md_priority = i - 1; To: md.md_priority = i - 1 + 100; This makes the first disk with a priority of 100 instead of 0, which makes it much easier to use "prefer" properly. > It's frustrating, it is *so* close to being workable with iscsi, and the > performance is very good, but if it is going to keep locking up on > me then I just cant use it that way :-( After failing many times with iSCSI, I use geom_gate with the following ggatec options: -t 30 -q 32768 -R 262144 -S 262144 -o rw It seems to be very reliable and fast, but you have to use "prefer" to get good performance, I only write across the network and not read. Load and round-robin lead to slow reads during periods of heavy writes. Hope that helps, - Andrew