Disk device groups enable volume manager disk groups to become “global” because it provides multipath and multihost support to the underlying disks. Each cluster node physically attached to the multihost disks provides a path to the disk device group.
In the Sun Cluster system, you can control multihost disks that are using Sun Cluster software by registering the multihost disks as disk device groups. This registration provides the Sun Cluster system with information about which nodes have a path to what volume manger disk groups. The Sun Cluster software creates a raw disk device group for each disk and tape device in the cluster. These cluster device groups remain in an offline state until you access them as global devices either by mounting a global file system or by accessing a raw database file.