Single System Image (SSI)

The features of a single system image include:

• Single User Interface: Users interact with the cluster through a single GUI.
• Single Process Space: Every user process holds a unique cluster-wide process ID. A process on a node creates a child process on the same or a completely different node. Communication between processes residing on different nodes is also possible.
• Single Entry Point: Users connect to multiple nodes in the cluster through a virtual host, which acts as single entry point. The connection request moves to different hosts to balance the entire load.
• Single I/O Space: This permits all nodes to perform I/O operations on local or remote disk devices.

The benefits of using a single system image include:

• It provides a similar syntax as that used in other systems, reducing operating errors.
• Users can work in their preferred interface, which is then altered by the administrator to manage the entire cluster as a single entity.
• It reduces cost of ownership and simplifies system management.
• It provides a straightforward view of all activities from a single node in the entire cluster.
• The end user is not concerned about where the application runs.
• It avoids using numerous skilled administrators, because only one is needed to centralize system management.
• It promotes standard tool development.
• It provides location-independent message communication.