Computer cluster

Technicians working on a large Linux cluster at the Chemnitz University of Technology, Germany
Sun Microsystems Solaris Cluster, with In-Row cooling
Taiwania series uses cluster architecture, with great capacity, helped scientists of Taiwan and many others during COVID-19
A simple, home-built Beowulf cluster.
A VAX 11/780, c. 1977
A load balancing cluster with two servers and N user stations.
A typical Beowulf configuration.
A NEC Nehalem cluster
Low-cost and low energy tiny-cluster of Cubieboards, using Apache Hadoop on Lubuntu
A pre-release sample of the Ground Electronics/AB Open Circumference C25 cluster computer system, fitted with 8x Raspberry Pi 3 Model B+ and 1x UDOO x86 boards.

Set of computers that work together so that they can be viewed as a single system.

- Computer cluster

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Grid computing

Use of widely distributed computer resources to reach a common goal.

A human computer, with microscope and calculator, 1952

Grid computing is distinguished from conventional high-performance computing systems such as cluster computing in that grid computers have each node set to perform a different task/application.

Distributed computing

Field of computer science that studies distributed systems.

(a), (b): a distributed system. (c): a parallel system.

Distributed programming typically falls into one of several basic architectures: client–server, three-tier, n-tier, or peer-to-peer; or categories: loose coupling, or tight coupling.


Multi-user, multiprocessing and virtual memory-based operating system.

OpenVMS V7.3-1 running the CDE-based DECwindows "New Desktop" GUI
OpenVMS V7.3-1 running the CDE-based DECwindows "New Desktop" GUI
Stylized "VAX/VMS" used by Digital
"Albert the Cheshire Cat" mascot for VAX/VMS, used by the DECUS VAX SIG
"Vernon the Shark" logo for OpenVMS
"Swoosh" logo used by HP for OpenVMS
The architecture of the OpenVMS operating system, demonstrating the layers of the system, and the access modes in which they typically run
VAXstation 4000 model 96 running OpenVMS V6.1, DECwindows Motif and the NCSA Mosaic browser
The "Grey Wall" of VAX/VMS documentation, at Living Computers: Museum + Labs
OpenVMS Alpha V8.4-2L1, showing the DCL CLI in a terminal session
VWS 4.5 running on top of VAX/VMS V5.5-2
DECwindows XUI window manager running on top of VAX/VMS V5.5-2

OpenVMS offers high availability through clustering — the ability to distribute the system over multiple physical machines.

Load balancing (computing)

In computing, load balancing refers to the process of distributing a set of tasks over a set of resources (computing units), with the aim of making their overall processing more efficient.

Diagram illustrating user requests to an Elasticsearch cluster being distributed by a load balancer. (Example for Wikipedia.)
Load balancing algorithm depending on divisibility of tasks
Master-Worker and bottleneck

In general, the processors each have an internal memory to store the data needed for the next calculations and are organized in successive clusters.

High-performance computing

The Center for Nanoscale Materials at the Advanced Photon Source

High-performance computing (HPC) uses supercomputers and computer clusters to solve advanced computation problems.

Clustered file system

File system which is shared by being simultaneously mounted on multiple servers.

An example of slack space, demonstrated with 4,096-byte NTFS clusters: 100,000 files, each five bytes per file, which equal to 500,000 bytes of actual data but require 409,600,000 bytes of disk space to store

There are several approaches to clustering, most of which do not employ a clustered file system (only direct attached storage for each node).


Digital electronic machine that can be programmed to carry out sequences of arithmetic or logical operations automatically.

A human computer, with microscope and calculator, 1952
The Ishango bone, a bone tool dating back to prehistoric Africa.
The Chinese suanpan (算盘). The number represented on this abacus is 6,302,715,408.
The Antikythera mechanism, dating back to ancient Greece circa 150–100 BC, is an early analog computing device.
A slide rule.
A portion of Babbage's Difference engine.
Sir William Thomson's third tide-predicting machine design, 1879–81
Replica of Konrad Zuse's Z3, the first fully automatic, digital (electromechanical) computer.
Colossus, the first electronic digital programmable computing device, was used to break German ciphers during World War II. It is seen here in use at Bletchley Park in 1943.
ENIAC was the first electronic, Turing-complete device, and performed ballistics trajectory calculations for the United States Army.
A section of the Manchester Baby, the first electronic stored-program computer
Bipolar junction transistor (BJT)
MOSFET (MOS transistor), showing gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
Diagram showing how a particular MIPS architecture instruction would be decoded by the control system
Magnetic-core memory (using magnetic cores) was the computer memory of choice in the 1960s, until it was replaced by semiconductor memory (using MOS memory cells).
Hard disk drives are common storage devices used with computers.
Cray designed many supercomputers that used multiprocessing heavily.
Replica of the Manchester Baby, the world's first electronic stored-program computer, at the Museum of Science and Industry in Manchester, England
A 1970s punched card containing one line from a Fortran program. The card reads: "Z(1) = Y + W(1)" and is labeled "PROJ039" for identification purposes.
The actual first computer bug, a moth found trapped on a relay of the Harvard Mark II computer
Visualization of a portion of the routes on the Internet

This term may also refer to a group of computers that are linked and function together, such as a computer network or computer cluster.


Computer with a high level of performance as compared to a general-purpose computer.

The IBM Blue Gene/P supercomputer "Intrepid" at Argonne National Laboratory runs 164,000 processor cores using normal data center air conditioning, grouped in 40 racks/cabinets connected by a high-speed 3D torus network.
Computing power of the top 1 supercomputer each year, measured in FLOPS
A circuit board from the IBM 7030
The CDC 6600. Behind the system console are two of the "arms" of the plus-sign shaped cabinet with the covers opened. Each arm of the machine had up to four such racks. On the right is the cooling system.
A Cray-1 preserved at the Deutsches Museum
A cabinet of the massively parallel Blue Gene/L, showing the stacked blades, each holding many processors
The CPU share of TOP500
Diagram of a three-dimensional torus interconnect used by systems such as Blue Gene, Cray XT3, etc.
The Summit supercomputer was as of November 2018 the fastest supercomputer in the world. With a measured power efficiency of 14.668 GFlops/watt it is also the third most energy efficient in the world.
An IBM HS20 blade
Wide-angle view of the ALMA correlator
Example architecture of a grid computing system connecting many personal computers over the internet
Top supercomputer speeds: logscale speed over 60 years
Top 20 supercomputers in the world (June 2014)
Taiwania 3 is a Taiwanese supercomputer which assisted the scientific community in fighting COVID-19. It was launched in 2020 and has a capacity of about two to three PetaFLOPS.
Distribution of TOP500 supercomputers among different countries, in November 2015

In another approach, many processors are used in proximity to each other, e.g. in a computer cluster.

Single system image

(a), (b): a distributed system. (c): a parallel system.

In distributed computing, a single system image (SSI) cluster is a cluster of machines that appears to be one single system.

Apache Hadoop

Collection of open-source software utilities that facilitates using a network of many computers to solve problems involving massive amounts of data and computation.

A multi-node Hadoop cluster

Hadoop was originally designed for computer clusters built from commodity hardware, which is still the common use.