How Sun Cluster Uses Shared Devices

Generally, if a node fails while providing access to a shared 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 shared 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 shared device on a cluster is the same as the API that is used to access a device locally.

Sun Cluster shared devices include disks, CD-ROMs, and tapes. However, disks are the only multiported shared 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 DID framework assigns a common (normalized) logical name 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.