Description
NSC provided a full single-system image cluster:
- Process migration
- Processes started on any node in the cluster could be migrated to any other node. Migration could be either manual or automatic (for load balancing).
- Single process space
- All processes were visible from all nodes in the cluster. The standard Unix process management commands (ps, kill and so on) were used for process management.
- Single root
- All files and directories were available from all nodes of the cluster
- Single I/O space
- All I/O devices were available from any node in the cluster. The normal device naming convention was modified to add a node number to all device names. For example the second serial port on node 3 would be
/dev/tty01h.3. A partition on a SCSI disk on node 2 might be /dev/rdsk/n2c3b0t4d0s3. - Single IPC space
- The standard UnixWare IPC mechanisms (shared memory, semaphores, message queues, Unix domain sockets) were all available for communication between processes running on any node.
- Cluster virtual IP address
- NSC provided a single IP address for access to the cluster from other systems. Incoming connections were load-balanced between the available cluster nodes.
The NSC system was designed for high availability—all system services were either redundant or would fail-over from one node to another in the advent of a node crash. The disk subsystem was either accessible from multiple nodes (using a Fibre Channel SAN or dual-ported SCSI) or used cross-node mirroring in a similar fashion to DRBD.
Read more about this topic: Unix Ware Non Stop Clusters
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