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

fault-tolerant Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...

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 presented ...

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

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

commodity hardware Commodity computing (also known as commodity cluster computing) involves the use of large numbers of already-available computing components for parallel computing, to get the greatest amount of useful computation at low cost. It is computing done i ...

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 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 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 servers in storage area networks (SAN) in commercial data cen ...

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. The SCSI standards define commands, protocols, electrical, optical and logical interface ...

) or used cross-node

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

in a similar fashion to

DRBD DRBD is a distributed replicated storage system for the Linux platform. It is implemented as a kernel driver, several userspace management applications, and some shell scripts. DRBD is traditionally used in high availability (HA) computer clust ...

History

NSC was developed for Tandem by

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 distributed operating system at UCLA. Locus was notable for commercializing sing ...

based on their Transparent Network Computing technology. During the lifetime of the project Locus were acquired by

Platinum Technology Platinum Technology Inc. was founded by Andrew Filipowski in 1987 to market and support deployment of database management software products and the applications enabled by database management technology and to render related services. Over its 12 ...

Inc. The NSC team and product were then transferred to Tandem. Initially NSC was developed for the

Compaq Compaq Computer Corporation (sometimes abbreviated to CQ prior to a 2007 rebranding) was an American information technology company founded in 1982 that developed, sold, and supported computers and related products and services. Compaq produced ...

Integrity XC packaged cluster, consisting of between two and six Compaq

ProLiant ProLiant is a brand of server computers that was originally developed and marketed by Compaq and currently marketed by Hewlett Packard Enterprise. After Compaq merged with Hewlett-Packard (HP), HP retired its NetServer brand in favor of the P ...

servers and one or two Compaq ServerNet switches to provide the cluster interconnect inter-node communication path. In this form NSC was commercialized by Compaq and only supported on qualified hardware from Compaq, and later Fujitsu-Siemens. In 2000 NSC was modified to allow standard Fast Ethernet 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 i ...

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 Reliant Motor Company was a British car manufacturer based in Tamworth, Staffordshire, England. It was founded in 1935 and ended car production in 2002, the company had been known as "Reliant Motor Company" (or RMC for short) until the 1990s w ...

clustering solution and in May 2001 Compaq announced that it would release a

GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general us ...

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