NSC was one of the first commercially available highly available clustering solutions for commodity hardware.
[1] NSC provided a full single-system image cluster: 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.
[3] This release of NSC was available on commodity PC hardware, although SCO recommended that systems with more than two nodes used the ServerNet interconnect.
After the sale of the SCO Unix business to Caldera Systems, it was announced that the long-term goal was to integrate the NSC product into the base UnixWare code[4] but this was not to be, Caldera Systems ceased distribution of NSC, replacing it by the Reliant HA clustering solution and in May 2001 Compaq announced that it would release a GPLed version of the NSC code, which eventually became OpenSSI.