From owner-freebsd-fs@FreeBSD.ORG Wed Aug 14 13:50:26 2013 Return-Path: Delivered-To: fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id A62BBB49 for ; Wed, 14 Aug 2013 13:50:26 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from smtp.digiware.nl (unknown [IPv6:2001:4cb8:90:ffff::3]) (using TLSv1 with cipher ADH-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 683E32C55 for ; Wed, 14 Aug 2013 13:50:26 +0000 (UTC) Received: from rack1.digiware.nl (unknown [127.0.0.1]) by smtp.digiware.nl (Postfix) with ESMTP id B416115343A for ; Wed, 14 Aug 2013 15:50:23 +0200 (CEST) X-Virus-Scanned: amavisd-new at digiware.nl Received: from smtp.digiware.nl ([127.0.0.1]) by rack1.digiware.nl (rack1.digiware.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id s0bNxbYlWZ5O; Wed, 14 Aug 2013 15:50:22 +0200 (CEST) Received: from [IPv6:2001:4cb8:3:1:1db2:7fa3:18b1:b05b] (unknown [IPv6:2001:4cb8:3:1:1db2:7fa3:18b1:b05b]) by smtp.digiware.nl (Postfix) with ESMTP id A0AFA153437 for ; Wed, 14 Aug 2013 15:50:22 +0200 (CEST) Message-ID: <520B8B1E.7060002@digiware.nl> Date: Wed, 14 Aug 2013 15:50:22 +0200 From: Willem Jan Withagen Organization: Digiware Management b.v. User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: fs@freebsd.org Subject: Fwd: Disk scheduling activity... X-Forwarded-Message-Id: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Aug 2013 13:50:26 -0000 Hi, Just a point of information or curiosity, and I don't think/know if it is any problem... I have the raidz array with 8 disks, which I'm using to backup to. It is configured 4 disks on a mvs controller 4 disks on an Areca controller (JBODs with battery) Both controllers are on a PCI-E slot dT: 1.366s w: 1.000s L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name 6 127 4 2 0.1 122 6481 18.8 56.5| da0 4 118 0 0 0.0 116 6646 19.6 56.5| da1 0 124 2 1 0.1 120 6650 19.0 56.6| da2 5 117 1 1 0.1 114 6726 20.0 56.5| da3 4 121 1 1 0.2 118 6895 25.7 70.6| ada0 2 115 1 0 30.0 113 7051 22.1 67.7| ada1 0 113 3 1 11.6 108 7057 26.3 73.7| ada2 3 105 1 0 10.6 103 6728 24.1 66.9| ada3 Most of the time the source just fully loads the pipe and sends 1Gbit/s. When that happens I see this alternating pattern of writing either to the 4 mvs disks, or writing to the Areca disks. But almost never are all disk accesses at the same time. And really never, never is there a mix of writing between the controller sets. I even made a little movie of it. :) http://www.tegenbosch28.nl./FreeBSD/disk-activity.mov What is in the disk scheduling that makes it this alternating pattern? And why are not both controllers writing (flushing?) at the same time. Changing the 4 ada?/mvs ports to ports on the motherboard behind a port-multiplier starts increasing the write time per disk, and thus increases the percentage that the disks are busy. So it is better to hang them off the mvs controller. --WjW