It is the
recommended way to deploy Xen domains in production. LVM can create "virtual"
disk partitions out of one or more physical hard drives and makes it possible to
dynamically group them into a virtual single chunk of storage. You can grow, shrink,
or move those partitions from drive to drive. You can even create larger partitions
than you could with a single drive.
The main components of LVM are as follows:
Physical volume: These are the hard disks or disk partitions that are visible
to the operating system. Each physical volume is in turn split up into smaller
chunks called physical extents (PEs).
Volume group: A volume group is an abstraction representing a collection of
physical volumes from which logical volumes can be created, thus combines
the two into one easy to administer unit of storage.
Logical volume: A logical volume is a virtual device and represents an
addressable consecutive space of block storage.
Physical extent: Each physical volume is divided into physical extents, each
of which is the same size as the logical extents for the volume group.
Logical extent: Each logical volume is split into logical extents.
Some of the main advantages of using LVM are as follows:
Ability to resize the volume groups.
Ability to resize logical volumes without taking down the server.
Ability to create read-only snapshots of logical volumes.
Ability to move logical volumes between physical volumes.
Ability to split or merge volume groups.
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