From owner-freebsd-current@FreeBSD.ORG Mon Dec 19 21:26:21 2011 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C8E3F106567B for ; Mon, 19 Dec 2011 21:26:21 +0000 (UTC) (envelope-from se@freebsd.org) Received: from nm30.bullet.mail.bf1.yahoo.com (nm30.bullet.mail.bf1.yahoo.com [98.139.212.189]) by mx1.freebsd.org (Postfix) with SMTP id 57F7A8FC12 for ; Mon, 19 Dec 2011 21:26:21 +0000 (UTC) Received: from [98.139.212.150] by nm30.bullet.mail.bf1.yahoo.com with NNFMP; 19 Dec 2011 21:26:20 -0000 Received: from [98.139.213.6] by tm7.bullet.mail.bf1.yahoo.com with NNFMP; 19 Dec 2011 21:26:20 -0000 Received: from [127.0.0.1] by smtp106.mail.bf1.yahoo.com with NNFMP; 19 Dec 2011 21:26:20 -0000 X-Yahoo-Newman-Id: 605905.77712.bm@smtp106.mail.bf1.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: Sm8uAmUVM1l_V.aeYjSz2YNju0l.oEB_y2L0rVEUc3jQ6LT 1gPym4JLQ__6jBgMSnDHJODeYNkhYzz5fbC9KzuwDOQe8uPM6xOxU6P8WKVN rSGNhvWpg_6E_k70zOkbKWA86Fy_xdQefeGQnWkmD501aQ8VLWDmv1mLsGav 5FZEFq_om_Za6C7ZiK9Nj5KqU9bFv2pANQfUuKt9hc5QQ2OdvqEQssRCphl3 KB_r_zyXNDlMP.wS9ZgJKUudy0eMZIWI9EoRmWdgxfdLVFh68JgQKeayoIO3 psU6Ehf7ClHZ0iEmLQSRhZDeMRDW8yZHlwZXEngl.NCcid._egh6eYhrubJY uWXteoZDKPfULR2s.ZgBZzTFJf3uGPxRDbDXrWUVr9B796i.cykg_awK0U42 4y83Zi2p8owjRsFc8 X-Yahoo-SMTP: iDf2N9.swBDAhYEh7VHfpgq0lnq. Received: from [192.168.119.20] (se@81.173.146.234 with plain) by smtp106.mail.bf1.yahoo.com with SMTP; 19 Dec 2011 13:26:20 -0800 PST Message-ID: <4EEFABFA.4090907@freebsd.org> Date: Mon, 19 Dec 2011 22:26:18 +0100 From: Stefan Esser User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20111105 Thunderbird/8.0 MIME-Version: 1.0 To: Garrett Cooper References: <4EEF488E.1030904@freebsd.org> <4EEFA472.5020509@freebsd.org> <0AE9C160-81EC-4A41-985B-EF63E4B0CD9B@gmail.com> In-Reply-To: <0AE9C160-81EC-4A41-985B-EF63E4B0CD9B@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: FreeBSD Current Subject: Re: Uneven load on drives in ZFS RAIDZ1 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 19 Dec 2011 21:26:21 -0000 Am 19.12.2011 22:00, schrieb Garrett Cooper: > On Dec 19, 2011, at 12:54 PM, Stefan Esser wrote: >> But it seems that others do not observe the asymmetric distribution of >> requests, which makes me wonder whether I happen to have meta data >> arranged in such a way that it is always read from ada0 or ada1, but not >> (or rarely) from ada2 or ada3. That could explain it, including the fact >> that raidz1 over other numbers of drives 8e.g. 3 or 6) apparently show a >> much more symmetric distribution of read requests. > > Basic question: does one set of drives vibrate differently than the other set? No: All drives are mounted in similar cages in a midi tower case (and since I did not like the temperature rising to 45C, last summer, I added case fans to keep the temperature of all drives equally low, too). But I'll try swapping drives (or rather SATA ports) tomorrow. If the drives are different (hardware or data on the drives), then the higher load will move, but if it's in the ZFS code, then I expect the higher request rate to stay on the first two drives. I'll report the outcome. (And repeating what I wrote before: The drives seem to behave perfectly well, they do just receive different numbers of read requests although the pool appears to be symmetric with regard to all factors that could have an impact. I really doubt this is caused by hardware, else there would be observable differences in latency or queue length.) Regards, STefan