Date: 25 Aug 2001 00:07:44 -0000 From: Mike Meyer <mwm@mired.org> To: FreeBSD-gnats-submit@freebsd.org Subject: docs/30062: [PATCH] The description of disk, slices and partitions lacks detail Message-ID: <20010825000744.55402.qmail@guru.mired.org>
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>Number: 30062
>Category: docs
>Synopsis: [PATCH] The description of disk, slices and partitions lacks detail
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-doc
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: doc-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Aug 24 17:10:00 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: Mike Meyer
>Release: FreeBSD 4.4-RC i386
>Organization:
Meyer Consulting
>Environment:
System: FreeBSD guru.mired.org 4.4-RC FreeBSD 4.4-RC #4: Sun Aug 19 11:29:30 CDT 2001 mwm@guru.mired.org:/sharetmp/obj/usr/src/sys/GURU i386
>Description:
The description of disk, slices and partitions doesn't provide any
detail. In particular, there are no examples, nor does it say where in
the device name the partition letter windsd up. I don't believe the
slice numbering for extension slices are detailed anywhere.
>How-To-Repeat:
Well, I noticed that there is lots of confusion about slice/partition
names on -questions, and on checking the handbook noticed that this
wasn't really addressed anywhere.
>Fix:
The following patch adds the missing information. It also notes that
drive numbers start at 0, and that USB mass storage devices are "da"
devices.
--- chapter.sgml-orig Fri Aug 24 18:29:16 2001
+++ chapter.sgml Fri Aug 24 18:58:22 2001
@@ -177,7 +177,7 @@
<literal>wcd</literal> before 4.0-RELEASE.</entry>
</row>
<row>
- <entry>SCSI hard drives</entry>
+ <entry>SCSI hard drives and USB Mass storage devices</entry>
<entry><literal>da</literal> from 3.0-RELEASE,
<literal>sd</literal> before 3.0-RELEASE.</entry>
</row>
@@ -223,6 +223,11 @@
</tgroup>
</table>
+ <para>All the drives attached through a specific driver are
+ numbered starting at 0. So the first IDE drive would be
+ <quote>ad<emphasis>0</emphasis></quote>. You seldom need to use
+ these devices.</para>
+
<sect2 id="slicesandpartitions">
<title>Slices and Partitions</title>
<indexterm><primary>slices</primary></indexterm>
@@ -231,17 +236,31 @@
<para>Physical disks usually contain
<firstterm>slices</firstterm>, unless they are
<quote>dangerously dedicated</quote>. Slice numbers follow
- the device name, prefixed with an <literal>s</literal>:
- <quote>da0<emphasis>s1</emphasis></quote>.</para>
+ the device name, prefixed with an <literal>s</literal>,
+ starting at 1. So <quote>da0<emphasis>s1</emphasis></quote>
+ is the first slice on the first SCSI drive. There can only be
+ four physical slices on a disk, but you can have logical
+ slices inside physical slices of the appropriate type. These
+ extended slices are numbered starting at 5, so
+ <quote>ad0<emphasis>s5</emphasis></quote> is the first
+ extended slice on a disk. These devices are used by file
+ systems that expect to occupy a slice.</para>
<para>Slices, <quote>dangerously dedicated</quote> physical
drives, and other drives contain
<firstterm>partitions</firstterm>, which are represented as
letters from <literal>a</literal> to <literal>h</literal>.
- <literal>b</literal> is reserved for swap partitions, and
- <literal>c</literal> is an unused partition the size of the
- entire slice or drive. This is explained in <xref
- linkend="disks-adding">.</para>
+ This letter is appended to the device name, so
+ <quote>da0<emphasis>a</emphasis></quote> is the a partition on
+ the first da drive, which is <quote>dangerously dedicated</quote>.
+ <quote>ad1s3<emphasis>e</emphasis></quote> is the fifth partition
+ in the third slice of the second IDE disk drive.</para>
+
+ <para>The boot code expects partition <literal>a</literal> to be
+ the root partition. Partition <literal>b</literal> is normally
+ reserved for swap partitions, and <literal>c</literal> is an
+ unused partition the size of the entire slice or drive. This
+ is explained in <xref linkend="disks-adding">.</para>
</sect2>
</sect1>
>Release-Note:
>Audit-Trail:
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