Volume Group Locks

• The metadata pertaining to the Logical Volumes and Physical Volumes in a Volume Group is stored at the Volume Group level. It is versioned with a checksum and changes are atomic.

• A Volume Group lock must be held while the metadata is accessed by a program.

• There are two modes of locks: VG_READ and VG_WRITE. A VG_WRITE lock is exclusive and prevents other processes holding the same lock simultaneously. Several processes can hold VG_READ locks concurrently.

• Conceptually, all Physical Volumes that do not belong to any real Volume Group are considered to belong to an Orphan Volume Group. So, for example, vgextend needs to hold a VG_WRITE lock on the Orphan Volume Group.