[7e1df8f9] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
|
---|
| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
---|
| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
|
---|
| 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
|
---|
| 5 | %general-entities;
|
---|
| 6 | ]>
|
---|
| 7 |
|
---|
| 8 | <sect1 id="aboutlvm">
|
---|
| 9 | <?dbhtml filename="aboutlvm.html"?>
|
---|
| 10 |
|
---|
| 11 | <sect1info>
|
---|
| 12 | <othername>$LastChangedBy$</othername>
|
---|
| 13 | <date>$Date$</date>
|
---|
| 14 | </sect1info>
|
---|
| 15 |
|
---|
| 16 | <title>About Logical Volume Management (LVM)</title>
|
---|
| 17 |
|
---|
[29244b7] | 18 | <para>
|
---|
| 19 | LVM manages disk drives. It allows multiple drives and partitions
|
---|
| 20 | to be combined into larger <emphasis>volume groups</emphasis>, assists in
|
---|
| 21 | making backups through a <emphasis>snapshot</emphasis>, and allows for
|
---|
| 22 | dynamic volume resizing. It can also provide mirroring similar to
|
---|
| 23 | a RAID 1 array.
|
---|
| 24 | </para>
|
---|
| 25 |
|
---|
| 26 | <para>
|
---|
| 27 | A complete discussion of LVM is beyond the scope of this introduction,
|
---|
| 28 | but basic concepts are presented below.
|
---|
| 29 | </para>
|
---|
| 30 |
|
---|
| 31 | <para>
|
---|
| 32 | To run any of the commands presented here, the <xref linkend='lvm2'/>
|
---|
| 33 | package must be installed. All commands must be run as the <systemitem
|
---|
| 34 | class="username">root</systemitem> user.
|
---|
| 35 | </para>
|
---|
| 36 |
|
---|
| 37 | <para>
|
---|
| 38 | Management of disks with lvm is accomplished using the following concepts:
|
---|
| 39 | </para>
|
---|
[7e1df8f9] | 40 |
|
---|
| 41 | <variablelist>
|
---|
| 42 | <varlistentry>
|
---|
| 43 | <term>physical volumes</term>
|
---|
[29244b7] | 44 | <listitem>
|
---|
| 45 | <para>
|
---|
| 46 | These are physical disks or partitions such as
|
---|
| 47 | /dev/sda3 or /dev/sdb.
|
---|
| 48 | </para>
|
---|
| 49 | </listitem>
|
---|
[7e1df8f9] | 50 | </varlistentry>
|
---|
| 51 |
|
---|
| 52 | <varlistentry>
|
---|
| 53 | <term>volume groups</term>
|
---|
[29244b7] | 54 | <listitem>
|
---|
| 55 | <para>
|
---|
| 56 | These are named groups of physical volumes that
|
---|
| 57 | can be manipulated by the administrator. The number of physical
|
---|
| 58 | volumes that make up a volume group is arbitrary. Physical volumes
|
---|
| 59 | can be dynamically added or removed from a volume group.
|
---|
| 60 | </para>
|
---|
| 61 | </listitem>
|
---|
[7e1df8f9] | 62 | </varlistentry>
|
---|
| 63 |
|
---|
| 64 | <varlistentry>
|
---|
| 65 | <term>logical volumes</term>
|
---|
[29244b7] | 66 | <listitem>
|
---|
| 67 | <para>
|
---|
| 68 | Volume groups may be subdivided into logical volumes. Each logical
|
---|
| 69 | volume can then be individually formatted as if it were a regular
|
---|
| 70 | Linux partition. Logical volumes may be dynamically resized by
|
---|
| 71 | the administrator according to need.
|
---|
| 72 | </para>
|
---|
| 73 | </listitem>
|
---|
[7e1df8f9] | 74 |
|
---|
| 75 | </varlistentry>
|
---|
[0d7900a] | 76 | </variablelist>
|
---|
[7e1df8f9] | 77 |
|
---|
[29244b7] | 78 | <para>
|
---|
| 79 | To give a concrete example, suppose that you have two 2 TB disks. Also
|
---|
| 80 | suppose a really large amount of space is required for a very large
|
---|
| 81 | database, mounted on <filename class='directory'>/srv/mysql</filename>.
|
---|
| 82 | This is what the initial set of partitions would look like:
|
---|
| 83 | </para>
|
---|
[7e1df8f9] | 84 |
|
---|
| 85 | <screen><literal>Partition Use Size Partition Type
|
---|
| 86 | /dev/sda1 /boot 100MB 83 (Linux)
|
---|
| 87 | /dev/sda2 / 10GB 83 (Linux)
|
---|
| 88 | /dev/sda3 swap 2GB 82 (Swap)
|
---|
| 89 | /dev/sda4 LVM remainder 8e (LVM)
|
---|
| 90 | /dev/sdb1 swap 2GB 82 (Swap)
|
---|
[0d7900a] | 91 | /dev/sdb2 LVM remainder 8e (LVM)</literal></screen>
|
---|
[7e1df8f9] | 92 |
|
---|
[29244b7] | 93 | <para>
|
---|
| 94 | First initialize the physical volumes:
|
---|
| 95 | </para>
|
---|
[7e1df8f9] | 96 |
|
---|
| 97 | <screen><userinput>pvcreate /dev/sda4 /dev/sdb2</userinput></screen>
|
---|
| 98 |
|
---|
[29244b7] | 99 | <note>
|
---|
| 100 | <para>
|
---|
| 101 | A full disk can be used as part of a physical volume, but
|
---|
| 102 | beware that the <command>pvcreate</command> command will destroy any
|
---|
| 103 | partition information on that disk.
|
---|
| 104 | </para>
|
---|
| 105 | </note>
|
---|
[20598a7] | 106 |
|
---|
[29244b7] | 107 | <para>
|
---|
| 108 | Next create a volume group named lfs-lvm:
|
---|
| 109 | </para>
|
---|
[7e1df8f9] | 110 |
|
---|
| 111 | <screen><userinput>vgcreate lfs-lvm /dev/sda4 /dev/sdb2</userinput></screen>
|
---|
| 112 |
|
---|
[29244b7] | 113 | <para>
|
---|
| 114 | The status of the volume group can be checked by running the command
|
---|
| 115 | <command>vgscan</command>. Now create the logical volumes. Since there
|
---|
| 116 | is about 3900 GB available, leave about 900 GB free for expansion. Note
|
---|
| 117 | that the logical volume named <emphasis>mysql</emphasis> is larger than
|
---|
| 118 | any physical disk.
|
---|
| 119 | </para>
|
---|
[7e1df8f9] | 120 |
|
---|
| 121 | <screen><userinput>lvcreate --name mysql --size 2500G lfs-lvm
|
---|
| 122 | lvcreate --name home --size 500G lfs-lvm</userinput></screen>
|
---|
| 123 |
|
---|
[29244b7] | 124 | <para>
|
---|
| 125 | Finally the logical volumes can be formatted and mounted. In this
|
---|
| 126 | example, the jfs file system (<xref linkend='jfsutils'/>) is used for
|
---|
| 127 | demonstration purposes.
|
---|
| 128 | </para>
|
---|
[7e1df8f9] | 129 |
|
---|
| 130 | <screen><userinput>mkfs -t ext4 /dev/lfs-lvm/home
|
---|
| 131 | mkfs -t jfs /dev/lfs-lvm/mysql
|
---|
| 132 | mount /dev/lfs-lvm/home /home
|
---|
| 133 | mkdir -p /srv/mysql
|
---|
| 134 | mount /dev/lfs-lvm/mysql /srv/mysql</userinput></screen>
|
---|
| 135 |
|
---|
[29244b7] | 136 | <para>
|
---|
| 137 | The LFS boot scripts automatically make these file systems available to
|
---|
| 138 | the system in the checkfs script. Edit the <filename>/etc/fstab</filename>
|
---|
| 139 | file as required to automatically mount them.
|
---|
| 140 | </para>
|
---|
| 141 |
|
---|
| 142 | <para>
|
---|
| 143 | A LVM logical volume can host a root filesystem, but requires the use
|
---|
| 144 | of an initramfs (initial RAM file system) and is not discussed here.
|
---|
| 145 | </para>
|
---|
| 146 |
|
---|
| 147 | <para>
|
---|
| 148 | For a more information about LVM, see the <ulink
|
---|
| 149 | url="http://www.tldp.org/HOWTO/LVM-HOWTO/">LVM HOWTO</ulink> and
|
---|
| 150 | the lvm man pages.
|
---|
| 151 | </para>
|
---|
[7e1df8f9] | 152 |
|
---|
| 153 | </sect1>
|
---|