From owner-svn-doc-all@FreeBSD.ORG Tue Nov 20 18:25:06 2012 Return-Path: Delivered-To: svn-doc-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 6A53E1EA; Tue, 20 Nov 2012 18:25:06 +0000 (UTC) (envelope-from eadler@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:1900:2254:2068::e6a:0]) by mx1.freebsd.org (Postfix) with ESMTP id 44DD18FC14; Tue, 20 Nov 2012 18:25:06 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.5/8.14.5) with ESMTP id qAKIP4m5071993; Tue, 20 Nov 2012 18:25:04 GMT (envelope-from eadler@svn.freebsd.org) Received: (from eadler@localhost) by svn.freebsd.org (8.14.5/8.14.5/Submit) id qAKIP4YR071991; Tue, 20 Nov 2012 18:25:04 GMT (envelope-from eadler@svn.freebsd.org) Message-Id: <201211201825.qAKIP4YR071991@svn.freebsd.org> From: Eitan Adler Date: Tue, 20 Nov 2012 18:25:04 +0000 (UTC) To: doc-committers@freebsd.org, svn-doc-all@freebsd.org, svn-doc-head@freebsd.org Subject: svn commit: r40110 - head/en_US.ISO8859-1/books/faq X-SVN-Group: doc-head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-doc-all@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "SVN commit messages for the entire doc trees \(except for " user" , " projects" , and " translations" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Nov 2012 18:25:06 -0000 Author: eadler Date: Tue Nov 20 18:25:04 2012 New Revision: 40110 URL: http://svnweb.freebsd.org/changeset/doc/40110 Log: Disk geometry stopped being a problem around 1997. Noted by: scottl Approved by: bcr (mentor) Modified: head/en_US.ISO8859-1/books/faq/book.xml Modified: head/en_US.ISO8859-1/books/faq/book.xml ============================================================================== --- head/en_US.ISO8859-1/books/faq/book.xml Tue Nov 20 18:24:58 2012 (r40109) +++ head/en_US.ISO8859-1/books/faq/book.xml Tue Nov 20 18:25:04 2012 (r40110) @@ -1476,81 +1476,6 @@ - - Which geometry should I use for a disk drive? - - - - - By the geometry of a disk, we mean - the number of cylinders, heads and sectors/track on a - disk. We will refer to this as C/H/S for convenience. - This is how the PC's BIOS works out which area on a disk - to read/write from. - - - This causes a lot of confusion among new system - administrators. First of all, the - physical geometry of a SCSI drive is - totally irrelevant, as &os; works in term of disk blocks. - In fact, there is no such thing as the - physical geometry, as the sector density varies across the - disk. What manufacturers claim is the physical - geometry is usually the geometry that they have - determined wastes the least space. For IDE disks, &os; does - work in terms of C/H/S, but all modern drives internally - convert this into block references. - - All that matters is the logical - geometry. This is the answer that the BIOS gets when it - asks the drive what is your geometry? It then - uses this geometry to access the disk. As &os; uses the - BIOS when booting, it is very important to get this right. - In particular, if you have more than one operating system on - a disk, they must all agree on the geometry. Otherwise you - will have serious problems booting! - - For SCSI disks, the geometry to use depends on whether - extended translation support is turned on in your controller - (this is often referred to as support for DOS disks - >1GB or something similar). If it is turned off, - then use N cylinders, 64 heads - and 32 sectors/track, where N is - the capacity of the disk in MB. For example, a 2 GB disk - should pretend to have 2048 cylinders, 64 heads and 32 - sectors/track. - - If it is turned on (it is often - supplied this way to get around certain limitations in - &ms-dos;) and the disk capacity is more than 1 GB, use - M cylinders, 63 sectors per track - (not 64), and 255 heads, where - M is the disk capacity in MB - divided by 7.844238 (!). So our example 2 GB drive - would have 261 cylinders, 63 sectors per track and 255 - heads. - - If you are not sure about this, or &os; fails to detect - the geometry correctly during installation, the simplest way - around this is usually to create a small DOS partition on - the disk. The BIOS should then detect the correct geometry, - and you can always remove the DOS partition in the partition - editor if you do not want to keep it. You might want to - leave it around for programming network cards and the like, - however. - - Alternatively, there is a freely available utility - distributed with &os; called - pfdisk.exe. You can find it in the - tools subdirectory on - the &os; CD-ROM or on the various &os; FTP sites. This - program can be used to work out what geometry the other - operating systems on the disk are using. You can then enter - this geometry in the partition editor. - - - - Are there any restrictions on how I divide the disk up? @@ -1606,8 +1531,8 @@ This is classically a case of &os; and some other - OS conflicting over their ideas of disk geometry. You will have to + OS conflicting over their ideas of disk + geometry. You will have to reinstall &os;, but obeying the instructions given above will almost always get you going.