LVM Features

Logical Volume Manager (LVM) is a storage management system that lets you allocate and manage disk space for file systems or raw data. Historically, you treated your disks individually and in terms of fixed-sized partitions; each disk or partition held a file system, swap space, boot area, or raw data. With LVM, you do not need to assign a disk or fixed-sized partition to a single purpose. Instead, consider the disks as a pool (or volume) of data storage, consisting of equal-sized extents. Extents are allocated into virtual storage devices known as logical volumes, which can be treated as disks.

LVM provides the following capabilities:

A logical volume size can be dynamically reduced or expanded to meet changing data needs. For example, a logical volume can be as small or large as the file system mounted to it requires. The file system can be extended without rebuilding it or the logical volume; reducing a file system is more complex, and may require recreating the file system.
Small chunks of unused space from several disks can be combined to create a usable volume.
A logical volume can exceed the size of a single physical disk. This feature is called disk spanning, because a single file system (and individual files) can span disks.
Up to six copies of identical data can be stored and updated simultaneously using LVM. This feature is called mirroring a logical volume, and requires an optional product, HP MirrorDisk/UX. See “Increasing Data Availability Through Mirroring”.
Mirrored data can be configured to automatically create a new mirror to a separate disk when one of the mirror copies fails. This feature is called sparing, and requires an optional product, HP MirrorDisk/UX. See “Increasing Disk Redundancy Through Disk Sparing”.
A logical volume can be created so that logically contiguous data blocks (for example, chunks of the same file) are distributed across multiple disks, which speeds I/O throughput for large files when they are read and written sequentially. This feature is called striping. Striping can be used in conjunction with mirroring. See “Increasing Performance Through Disk Striping”.
Devices accessed through multiple links can be configured to improve availability. If the primary link to a device fails, LVM can switch automatically to an alternate link. This feature is called multipathing. See “Increasing Hardware Path Redundancy Through Multipathing”.

LVM Features

Technical documentation

» Table of Contents

» Glossary

» Index