LVM 逻辑卷
LVM：Logical Volume Management 逻辑卷管理LVM is built on the hard disk and partition a logical layer to increase the flexibility of the disk partition management.
Traditional Disk Management:
We are the top direct access to the file system, so that the underlying physical disk reads.
lvm works:
The underlying disk is encapsulated in a logical way (logical volume) is presented to the upper application, logical volume where you can easily add and delete hard disk partitions.
PV (Physical Volume) - physical volume
Physical volumes at the lowest level in the logical volume management, it may be actual physical partitions on the hard disk (e.g. sdb1), may be an entire physical hard disk (e.g. SDC), it may be a raid devices (e.g. md0).
VG (Volume Group) - Volume Group
Volume group based on the physical volume, a volume group comprising at least one physical volume, physical volume can be dynamically added to the volume group after the establishment of the volume group. A logical volume management system project can have only one volume group can have more than one volume group.
LV (Logical Volume) - Logical Volume
Logical volume based on the volume group, unallocated space in the volume group can be used to create a new logical volume, can reduce the space dynamically expand and establish the logical volume. A plurality of logical volumes in the system can belong to the same volume group, may belong to different groups of the plurality of volumes.