Date: Tue, 20 Nov 2012 18:25:04 +0000 (UTC) From: Eitan Adler <eadler@FreeBSD.org> 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 Message-ID: <201211201825.qAKIP4YR071991@svn.freebsd.org>
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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 @@ </qandaentry> <qandaentry> - <question id="geometry"> - <para>Which geometry should I use for a disk drive?</para> - </question> - - <answer> - <note> - <para>By the <quote>geometry</quote> 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.</para> - </note> - - <para>This causes a lot of confusion among new system - administrators. First of all, the - <emphasis>physical</emphasis> geometry of a SCSI drive is - totally irrelevant, as &os; works in term of disk blocks. - In fact, there is no such thing as <quote>the</quote> - physical geometry, as the sector density varies across the - disk. What manufacturers claim is the <quote>physical - geometry</quote> 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.</para> - - <para>All that matters is the <emphasis>logical</emphasis> - geometry. This is the answer that the BIOS gets when it - asks the drive <quote>what is your geometry?</quote> 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!</para> - - <para>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 <quote>support for DOS disks - >1GB</quote> or something similar). If it is turned off, - then use <replaceable>N</replaceable> cylinders, 64 heads - and 32 sectors/track, where <replaceable>N</replaceable> 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.</para> - - <para>If it <emphasis>is</emphasis> 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 - <replaceable>M</replaceable> cylinders, 63 sectors per track - (<emphasis>not</emphasis> 64), and 255 heads, where - <replaceable>M</replaceable> 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.</para> - - <para>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.</para> - - <para>Alternatively, there is a freely available utility - distributed with &os; called - <filename>pfdisk.exe</filename>. You can find it in the - <filename class="directory">tools</filename> 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.</para> - </answer> - </qandaentry> - - <qandaentry> <question id="disk-divide-restrictions"> <para>Are there any restrictions on how I divide the disk up?</para> @@ -1606,8 +1531,8 @@ <answer> <para>This is classically a case of &os; and some other - OS conflicting over their ideas of disk <link - linkend="geometry">geometry</link>. 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.</para> </answer>
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