NonStop Clusters (NSC) was an add-on package for SCO UnixWare that allowed creation of

fault-tolerant Fault tolerance is the ability of a system to maintain proper operation despite failures or faults in one or more of its components. This capability is essential for high-availability, mission-critical, or even life-critical systems. Fault to ...

single-system image In distributed computing, a single system image (SSI) cluster is a cluster of machines that appears to be one single system. The concept is often considered synonymous with that of a distributed operating system, but a single image may be presente ...

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Cluster II (spacecraft), a European Space Agency mission to study the magnetosphere * Asteroid cluster, a small ...

s of machines running UnixWare. NSC was one of the first commercially available highly available clustering solutions for commodity hardware.

Description

NSC provided a full

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,

semaphore Semaphore (; ) is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arra ...

s, message queues,

Unix domain socket A Unix domain socket (UDS), a.k.a. local socket, a.k.a. inter-process communication (IPC) socket, is a communication endpoint for exchanging data between processes executing in the same Unix or Unix-like operating system. The name, ''Unix domain ...

s) 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 High availability (HA) is a characteristic of a system that aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period. There is now more dependence on these systems as a result of modernization ...

—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 Fibre Channel (FC) is a high-speed data transfer protocol providing in-order, lossless delivery of raw block data. Fibre Channel is primarily used to connect computer data storage to Server (computing), servers in storage area networks (SAN) in ...

SAN or dual-ported

SCSI Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices, best known for its use with storage devices such as hard disk drives. SCSI was introduced ...

) or used cross-node

mirroring Mirroring is the behavior in which one person subconsciously imitates the gesture, idiolect, speech pattern, or attitude of another. Mirroring often occurs in social situations, particularly in the company of close friends or family, often going ...

in a similar fashion to

DRBD Distributed Replicated Block Device (DRBD) is a distributed replicated storage system for the Linux platform. It mirrors block devices between multiple hosts, functioning transparently to applications on the host systems. This replication can inv ...

History

NSC was developed for

Tandem Computers Tandem Computers, Inc. was the dominant manufacturer of fault-tolerant computer systems for Automated teller machine, ATM networks, banks, stock exchanges, telephone switching centers, 911 systems, and other similar commercial transaction proc ...

Locus Computing Corporation Locus Computing Corporation was formed in 1982 by Gerald J. Popek, Charles S. Kline and Gregory I. Thiel to commercialize the technologies developed for the LOCUS (operating system), LOCUS distributed computing, distributed operating system at UCL ...

based on their Transparent Network Computing technology. During the lifetime of the project Locus were acquired by Platinum Technology Inc. The NSC team and product were then transferred to Tandem. Initially NSC was developed for the

Compaq Compaq Computer Corporation was an American information technology, information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced some of the first IBM PC compati ...

Integrity XC packaged cluster, consisting of between two and six Compaq ProLiant servers and one or two Compaq

ServerNet ServerNet is a switched fabric communications link primarily used in proprietary computers made by Tandem Computers, Compaq, and HP. Its features include good scalability, clean fault containment, error detection and failover. The ServerNet arch ...

switches to provide the cluster interconnect inter-node communication path. In this form NSC was commercialized by the Tandem Computers division of Compaq and only supported on qualified hardware from Compaq, and later

Fujitsu-Siemens Fujitsu Siemens Computers GmbH was a Japanese and German vendor of information technology. The company was founded in 1999 as a 50/50 joint venture between Fujitsu of Japan and Siemens AG of Germany. On April 1, 2009, the company became Fujitsu ...

. In 2000, NSC was modified to allow standard

Fast Ethernet In computer networking, Fast Ethernet Ethernet physical layer, physical layers carry traffic at the nominal rate of . The Classic Ethernet, prior Ethernet speed was . Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. ...

and later

Gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use in ...

switches as the cluster interconnect and commercialized by SCO as UnixWare NonStop Clusters 7.1.1+IP. 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 Caldera International, Inc., earlier Caldera Systems, was an American software company that existed from 1998 to 2002 and developed and sold Linux- and Unix-based operating system products. Caldera Systems was created in August 1998 as a spinoff ...

, it was announced that the ''long-term goal'' was to integrate the NSC product into the base UnixWare code 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

GPL The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first c ...

ed version of the NSC code, which eventually became

OpenSSI OpenSSI is an open-source single-system image clustering system. It allows a collection of computers to be treated as one large system, allowing applications running on any one machine access to the resources of all the machines in the cluster ...

. .

References

{{DEFAULTSORT:Unixware Nonstop Clusters Cluster computing Internet Protocol based network software High-availability cluster computing