From owner-freebsd-performance@FreeBSD.ORG Mon Dec 17 21:44:21 2012 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D82DEE24 for ; Mon, 17 Dec 2012 21:44:21 +0000 (UTC) (envelope-from dieterbsd@engineer.com) Received: from mailout-us.gmx.com (mailout-us.gmx.com [74.208.5.67]) by mx1.freebsd.org (Postfix) with SMTP id 744818FC14 for ; Mon, 17 Dec 2012 21:44:21 +0000 (UTC) Received: (qmail 5046 invoked by uid 0); 17 Dec 2012 21:44:14 -0000 Received: from 67.206.184.86 by rms-us005 with HTTP Content-Type: text/plain; charset="utf-8" Date: Mon, 17 Dec 2012 16:44:11 -0500 From: "Dieter BSD" Message-ID: <20121217214413.263570@gmx.com> MIME-Version: 1.0 Subject: FFS - Still using rotational delay with modern disks? To: freebsd-fs@freebsd.org,freebsd-performance@freebsd.org X-Authenticated: #74169980 X-Flags: 0001 X-Mailer: GMX.com Web Mailer x-registered: 0 Content-Transfer-Encoding: 8bit X-GMX-UID: eve9cJEH3zOlNR3dAHAh+cZ+IGRvb0Ci X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 Dec 2012 21:44:21 -0000 The newfs man page says: -a maxcontig Specify the maximum number of contiguous blocks that will be laid out before forcing a rotational delay.  The default value is 16. See tunefs(8) for more details on how to set this option. Is this still a good idea with modern drives where the number of sectors per track varies, and no one but the manufacturer knows how many sectors a particular track has? [1] Skipping sectors could unnecessarily force a seek to the next track, thus hurting rather than helping performance. I have to wonder if FreeBSD even supports any hard drives that don't use zone bit recording? The tunefs man page does not mention this parameter. [1] http://en.wikipedia.org/wiki/Zone_bit_recording