Device groups enable volume manager disk groups to become “shared” because they provide multipath and multihost support to the underlying disks. Each cluster Solaris host that is physically attached to the multihost disks provides a path to the device group.
In the Sun Cluster system, you can control multihost disks that are using Sun Cluster software by registering the multihost disks as device groups. This registration provides the Sun Cluster system with information about which nodes have a path to which volume manager disk groups. The Sun Cluster software creates a raw 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 shared devices either by mounting a cluster file system or by accessing a raw database file.