Volumes are assigned to volume groups, and volume groups are mapped to host attachments.
For example, Host System A has two host attachments and Host System B has one host attachment. Each host attachment is mapped to one or more volume groups, which contain several volumes, and a specific volume group can be accessed by more than one host attachment. In this example, volumes 5 and 6 are in Volume Group 2 and Volume Group 3, so they can be accessed by both host systems.