What is the difference between a physical volume and a volume group in the LVM system?

In the LVM (Logical Volume Manager) system, a Physical Volume (PV) is a real physical data carrier, such as a hard disk or a disk partition, that is initialized for use in LVM.

A Volume Group (VG) is a collection of one or more physical volumes into a single storage pool. VG provides space for creating Logical Volumes (LV), which are used by the system as regular partitions.

In other words:

• A physical volume is a basic physical resource (disk or partition).
• A volume group is an abstraction that combines several physical volumes for flexible space management.

Example:

• /dev/sda1 and /dev/sdb1 are physical volumes
• They are combined into a volume group vg_data
• Logical volumes such as lv_home, lv_var, etc., are created from vg_data.