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NonStop Clusters (NSC) was an add-on package for SCO UnixWare that allowed creation of fault-tolerant single-system image clusters of machines running UnixWare. NSC was one of the first commercially available highly available clustering solutions for commodity hardware. 〔 〕 ==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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「UnixWare NonStop Clusters」の詳細全文を読む スポンサード リンク
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