Logical Volume Management is a technology that allows data to be stored across several different hard disks, transparently to the end user. It is designed to solve problems that occur when a hard disk partition fills up, making adding and removing storage, resizing partitions and generally mucking around with your storage much easier.
LVM introduces several potentially confusing new pieces of terminology to describe the structure of how data can be stored over several physical hard disks. The following graphic was originally from http://www.ccp-west.de/tipps.html and shows where each of these terms applies.
As you can see, one or more "physical volumes" (or hard drives to you and me!) are added to a "volume group". All the physcial volumes in a volume group can be treated rather like one giant hard drive, with a capacity of the sum of the physical volumes that constitute it. It is even possible to add further hard drives to the volume group in the future, expanding its capacity. One or more "logical volumes" are then created on top of the volume group. Logical volumes are, in some ways, analogous to the partitions in a standard partitioning scheme. They do not have to take up all the space available in the volume group and act as "containers" for the filesystems that hold the data. The big difference between logical volumes and normal disk partitions is that these are dynamically re-sizeable and can be worked on whilst mounted. On top of the logical volumes, you can then create filesystems that you can mount on your Linux system and fill with data as normal.
Step By Step
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