LVM manages disk drives. It allows multiple drives and partitions to be combined into larger volume groups, assists in making backups through a snapshot, and allows for dynamic volume resizing. It can also provide mirroring similar to a RAID 1 array.
A complete discussion of LVM is beyond the scope of this introduction, but basic concepts are presented below.
To run any of the commands presented here, the LVM2-2.02.116 package must be
installed. All commands must be run as the root user.
Management of disks with lvm is accomplished using the following concepts:
These are physical disks or partitions such as /dev/sda3 or /dev/sdb.
These are named groups of physical volumes that can be manipulated by the administrator. The number of physical volumes that make up a volume group is arbitrary. Physical volumes can be dynamically added or removed from a volume group.
Volume groups may be subdivided into logical volumes. Each logical volume can then be individually formatted as if it were a regular Linux partition. Logical volumes may be dynamically resized by the administrator according to need.
To give a concrete example, suppose that you have two 2 TB disks.
Also suppose a really large amount of space is required for a very
large database, mounted on /srv/mysql.
This is what the initial set of partitions would look like:
Partition Use Size Partition Type
/dev/sda1 /boot 100MB 83 (Linux)
/dev/sda2 / 10GB 83 (Linux)
/dev/sda3 swap 2GB 82 (Swap)
/dev/sda4 LVM remainder 8e (LVM)
/dev/sdb1 swap 2GB 82 (Swap)
/dev/sdb2 LVM remainder 8e (LVM)
First initialize the physical volumes:
pvcreate /dev/sda4 /dev/sdb2
Next create a volume group named lfs-lvm:
vgcreate lfs-lvm /dev/sda4 /dev/sdb2
The status of the volume group can be checked by running the command vgscan. Now create the logical volumes. Since there is about 3900 GB available, leave about 900 GB free for expansion. Note that the logical volume named mysql is larger than any physical disk.
lvcreate --name mysql --size 2500G lfs-lvm lvcreate --name home --size 500G lfs-lvm
Finally the logical volumes can be formatted and mounted. In this example, the jfs file system (jfsutils-1.1.15) is used for demonstration purposes.
mkfs -t ext4 /dev/lfs-lvm/home mkfs -t jfs /dev/lfs-lvm/mysql mount /dev/lfs-lvm/home /home mkdir -p /srv/mysql mount /dev/lfs-lvm/mysql /srv/mysql
The LFS boot scripts automatically make these file systems available
to the system in the checkfs script. Edit the /etc/fstab file as required to automatically mount
them.
A LVM logical volume can host a root filesystem, but requires the use of an initramfs (initial RAM file system) and is not discussed here.
For a more information about LVM, see the LVM HOWTO and the lvm man pages.
Last updated on 2013-02-11 13:51:17 -0500