From owner-freebsd-questions@FreeBSD.ORG Fri Jul 6 21:13:05 2012 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6D10E106564A for ; Fri, 6 Jul 2012 21:13:05 +0000 (UTC) (envelope-from vrwmiller@gmail.com) Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com [209.85.214.182]) by mx1.freebsd.org (Postfix) with ESMTP id 31BDD8FC0A for ; Fri, 6 Jul 2012 21:13:05 +0000 (UTC) Received: by obbun3 with SMTP id un3so19545650obb.13 for ; Fri, 06 Jul 2012 14:13:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; bh=maUp3d5MQi7++ejwoiztRYEXR9tbR7a9qxyX3Ns/MS4=; b=AHLX6txMrABGGOjGESUx7BEXMca7p46UtlFrdVTqAHnMNofe9zeLRtUfpzYxsBBAsy zF7ysaRXTFS8vcwIEDdUMM21WA+ejCod0VbUv81Geg8NneXATVqoJw69CFZJw7crz/HS +SE8lKssy+jgVAGEtbUlv6B+2GIy/j6ALzBFijx96jaYADtAM+SE2dAapor30QikIjdA lHDIsewS/H9/KORtl3zIvuWDqhR7DVUjiMiHzdmW9bjRVsCNOYLkEX9oXNLzJ2hjbidY HJuuWFV7AtBz6t8oiyJnBbnH9CnY3FZPvJj3pqXluaLFqEm98bddk3Wbo/JHD4vfLxRb rj0g== MIME-Version: 1.0 Received: by 10.182.216.99 with SMTP id op3mr5888561obc.30.1341609184420; Fri, 06 Jul 2012 14:13:04 -0700 (PDT) Sender: vrwmiller@gmail.com Received: by 10.182.10.34 with HTTP; Fri, 6 Jul 2012 14:13:04 -0700 (PDT) In-Reply-To: References: Date: Fri, 6 Jul 2012 17:13:04 -0400 X-Google-Sender-Auth: tumg9nluCKGLUeqi85RCGZ24t0c Message-ID: From: Rick Miller To: FreeBSD Questions Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: Does FreeBSD start slices at head boundaries? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Jul 2012 21:13:05 -0000 I went through this exercise to determine if there were boundary issues installing FreeBSD on disks. I concluded that FreeBSD was indeed installing at head boundaries. A colleague then pointed me to http://ivoras.net/blog/tree/2011-01-01.freebsd-on-4k-sector-drives.html which calls into question whether sysinstall and fdisk really are installing FreeBSD's slice at the 64th cylinder. Should I be concerned with this? This came about due to a scenario where Linux would start its filesystem at sector 63, right before the head boundary. On I/O intensive applications, it was common for reads/write to cross the head boundary resulting in unnecessary disk thrashing and long I/O wait times. The issue was corrected in Linux by changing the start cylinder to 2048. Some theorized that FreeBSD was vulnerable to this scenario. Thoughts/feedback? On Fri, Jul 6, 2012 at 11:09 AM, Rick Miller wrote: > Hi All, > > Installing FreeBSD 8.x I select "A" at the fdisk partition editor to > use the entire disk. It creates an unused slice with offset 0 and 63 > sectors in size. Then partition 1 starts at sector 63 and utilizes > the remaining disk space. Does sysinstall's diskPartitonEditor macro > automatically start partitions at head boundaries? The reason I ask > is because I am most familiar with sector 64 being the start of a head > boundary as opposed to 63. Is my understanding incorrect? > > -- > Take care > Rick Miller -- Take care Rick Miller