How Sun Cluster Uses Global Devices

Generally, if a node fails while providing access to a global device, the Sun Cluster software switches over to another path to the device and redirects the access to that path. This redirection is easy with global devices because the same name is used for the device regardless of the path. Access to a remote device is performed in the same way as on a local device that uses the same name. Also, the API to access a global device on a cluster is the same as the API that is used to access a device locally.

Sun Cluster global devices include disks, CD-ROMs, and tapes. However, disks are the only multiported global devices that are supported. This limited support means that CD-ROM and tape devices are not currently highly available devices. The local disks on each server are also not multiported, and thus are not highly available devices.

The cluster assigns unique IDs to each disk, CD-ROM, and tape device in the cluster. This assignment enables consistent access to each device from any node in the cluster.