Logical Volume Manager for Linux

The Logical Volume Manager, or LVM, is widely used on commercial UNIX systems for online disk storage management. It adds an extra layer between kernel I/O and physical disk devices. In the traditional disk storage schemes, the disk is partitioned into fixed size segments. The LVM considers all installed disks as pools of data storage. Each disk is called a Physical Volume (PV) and is part of one pool of data storage known as a Volume Group (VG). A volume group may consist of multiple physical disks and is represented as one large storage space. The volume group is then divided into partitions called Logical Volumes (LV). A logical volume acts as one logical disk partition, although it can span multiple physical disks. Its size can be increased/decreased without any loss of data. A disk may be added to a volume group at any time when there is a need to increase data storage capacity. This provides a great flexibility for changing storage space demands and is useful for combining multiple small capacity disks into one large logical storage space.

HP-UX and Digital UNIX use the OSF version of LVM, while Solaris uses Veritas. Linux LVM was recently released and is similar to the LVM used on HP-UX. As Linux penetrates into business, use of LVM is inevitable in Linux systems. The LVM support has been included in new kernel versions. This article describes how to install, configure, and use the Linux version of LVM. I'll begin with a brief introduction for those who have not used LVM with other platforms. If you're familiar with LVM, you may wish to skip this introduction. All steps from download to installation and management of LVM will be presented in the article. For example configurations in this article, I have used a PC with three IDE disks. The first disk contains a traditional Linux installation, while the other two disks, each of 200-MB capacity, are used with LVM.