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In the previous chapter we looked at adding a new disk drive to a Fedora system, creating a partition and file system and then mounting that file system so that the disk can be accessed. An alternative to creating fixed partitions and file systems is to use Logical Volume Management (LVM) to create logical disks made of space from one or more physical disks or partitions. The advantage of using LVM is that space can be added to or removed from logical volumes as needed without the need to spread data over multiple file systems.
Let us take, for example, the root (/) file system. Without LVM this filesystem would be created with a certain size when the operating is installed. If a new disk drive is installed there is no way to allocate any of that space to the / filesystemfile system. The only option would be to create new filesystems file systems on the new disk and mount it at a particular mount point. In this scenario you would have plenty of space on the new filesystem by file system but the / filesystem file system would still be nearly full. The only option would be to move files onto the new filesystemfile system. With LVM, the new disk (or part thereof) can be assigned to the logical volume contain containing the root file system thereby extending the space available.
In this chapter we will look at the steps necessary to add new disk space to both a volume group and a logical volume for the purpose of adding additional space to the root file system.
== An Overview of Logical Volume Management (LVM) ==
LVM provides a flexible and high level approach to managing disk space. Instead of each disk drive being split into partitions of fixed sizes onto which fixed size are in turn file systems are created, LVM provides a way to group together disk space into logical volumes which can be easily resized and moved. In additional addition LVM allows administrators to carefully control disk space assigned to different groups of users by allocating distinct volume groups or logical volumes to those users. When the space initially allocated to the volume is exhausted the administrator can simply add more space without having to move the user files to a different file system.
LVM consists of the following components:
=== Logical Volume (LV) ===
A logical volume is the equivalent to a disk partition and, as with a disk partition, can contain a filesystemfile system.
=== Physical Extent (PE) ===
