A computer cluster is a group of linked computers A computer is a programmable machine that receives input, stores and manipulates data//information, and provides output in a useful format, working together closely so that in many respects they form a single computer. The components of a cluster are commonly, but not always, connected to each other through fast local area networks A local area network is a computer network covering a small physical area, like a home, office, or small groups of buildings, such as a school, or an airport. The defining characteristics of LANs, in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased. Clusters are usually deployed to improve performance and/or availability over that of a single computer, while typically being much more cost-effective than single computers of comparable speed or availability.[1]

Contents

Cluster categorizations

High-availability (HA) clusters

High-availability clusters High-availability clusters are computer clusters that are implemented primarily for the purpose of providing high availability of services which the cluster provides. They operate by having redundant computers or nodes which are then used to provide service when system components fail. Normally, if a server with a particular application crashes, (also known as Failover Clusters) are implemented primarily for the purpose of improving the availability of services that the cluster provides. They operate by having redundant nodes In communication networks, a node is a connection point, either a redistribution point or a communication endpoint (some terminal equipment). The definition of a node depends on the network and protocol layer referred to. A physical network node is an active electronic device that is attached to a network, and is capable of sending, receiving, or, which are then used to provide service when system components fail. The most common size for an HA cluster is two nodes, which is the minimum requirement to provide redundancy. HA cluster implementations attempt to use redundancy of cluster components to eliminate single points of failure A Single Point of Failure, , is a part of a system which, if it fails, will stop the entire system from working . They are undesirable in any system whose goal is high availability, be it a network, software application or other industrial system.

There are commercial implementations of High-Availability clusters for many operating systems. The Linux-HA project is one commonly used free software Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with minimal restrictions only to ensure that further recipients can also do these things and that manufacturers of consumer- HA package for the Linux Linux refers to the family of Unix-like computer operating systems using the Linux kernel. Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers. Linux is predominantly known for its use in servers; in 2009 it held a server market share operating system.

Load-balancing clusters

Load-balancing In computer networking, load balancing is a technique to distribute workload evenly across two or more computers, network links, CPUs, hard drives, or other resources, in order to get optimal resource utilization, maximize throughput, minimize response time, and avoid overload. Using multiple components with load balancing, instead of a single is when multiple computers are linked together to share computational workload or function as a single virtual computer. Logically, from the user side, they are multiple machines, but function as a single virtual machine. Requests initiated from the user are managed by, and distributed among, all the standalone computers to form a cluster. This results in balanced computational work among different machines, improving the performance of the cluster systems.

Compute clusters

Often clusters are used primarily for computational purposes, rather than handling IO-oriented operations such as web service or databases. For instance, a cluster might support computational simulations of weather or vehicle crashes. The primary distinction within compute clusters is how tightly-coupled the individual nodes are. For instance, a single compute job may require frequent communication among nodes - this implies that the cluster shares a dedicated network, is densely located, and probably has homogenous nodes. This cluster design is usually referred to as Beowulf Cluster. The other extreme is where a compute job uses one or few nodes, and needs little or no inter-node communication. This latter category is sometimes called "Grid" computing. Tightly-coupled compute clusters are designed for work that might traditionally have been called "supercomputing". Middleware such as MPI (Message Passing Interface) or PVM (Parallel Virtual Machine) permits compute clustering programs to be portable to a wide variety of clusters.

Grid computing

Main article: Grid computing Grid computing is a term referring to the combination of computer resources from multiple administrative domains to reach common goal. What distinguishes grid computing from conventional high performance computing systems such as cluster computing is that grids tend to be more loosely coupled, heterogeneous, and geographically dispersed. It is

Grids are usually computer clusters, but more focused on throughput like a computing utility Utility computing is the packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility . This system has the advantage of a low or no initial cost to acquire hardware; instead, computational resources are essentially rented. Customers with very large computations or a sudden peak in rather than running fewer, tightly-coupled jobs. Often, grids will incorporate heterogeneous collections of computers, possibly distributed geographically, sometimes administered by unrelated organizations.

Grid computing is optimized for workloads which consist of many independent jobs or packets of work, which do not have to share data between the jobs during the computation process. Grids serve to manage the allocation of jobs to computers which will perform the work independently of the rest of the grid cluster. Resources such as storage may be shared by all the nodes, but intermediate results of one job do not affect other jobs in progress on other nodes of the grid.

An example of a very large grid is the Folding@home Folding@home (sometimes abbreviated as FAH or F@h) is a distributed computing (DC) project designed to perform computationally intensive simulations of protein folding and other molecular dynamics (MD), and to improve on the methods available to do so. It was launched on October 1, 2000, and is currently managed by the Pande Group, within Stanford project. It is analyzing data that is used by researchers to find cures for diseases such as Alzheimer's and cancer. Another large project is the SETI@home SETI@home is a volunteer computing project using Internet-connected computers, hosted by the Space Sciences Laboratory, at the University of California, Berkeley, in the United States. SETI is an acronym for the Search for Extra-Terrestrial Intelligence. Its purpose is to analyze radio signals, searching for signs of extra terrestrial intelligence project, which may be the largest distributed grid in existence. It uses approximately three million home computers all over the world to analyze data from the Arecibo Observatory The Arecibo Observatory is a radio telescope located close to the city of Arecibo in Puerto Rico. It is operated by Cornell University under cooperative agreement with the National Science Foundation. The observatory works as the National Astronomy and Ionosphere Center although both names are officially used to refer to it. NAIC more properly radiotelescope, searching for evidence of extraterrestrial intelligence. In both of these cases, there is no inter-node communication or shared storage. Individual nodes connect to a main, central location to retrieve a small processing job. They then perform the computation and return the result to the central server. In the case of the @home projects, the software is generally run when the computer is otherwise idle. U of C Berkley has developed an open source application BOINC The Berkeley Open Infrastructure for Network Computing is a non-commercial middleware system for volunteer and grid computing. It was originally developed to support the SETI@home project before it became useful as a platform for other distributed applications in areas as diverse as mathematics, medicine, molecular biology, climatology, and to allow individual users to contribute to the above and other projects such as lhc@home (Large Hadron Collider The Large Hadron Collider is the world's largest and highest-energy particle accelerator, intended to collide opposing particle beams of either protons at an energy of 7 teraelectronvolts (1.12 microjoules) per particle, or lead nuclei at an energy of 574 TeV (92.0 µJ) per nucleus. The term hadron refers to particles composed of quarks. It is) from a single manager which can then be set to allocate a percentage of idle time to each of the projects a node is signed up for. The Software can be downloaded and a project list can be found here BOINC

The grid setup means that the nodes can take however many jobs they are able to process in one session and then return the results and acquire a new job from a central project server.

Implementations

The TOP500 The TOP500 project ranks and details the 500 most powerful known computer systems in the world. The project was started in 1993 and publishes an updated list of the supercomputers twice a year. The project aims to provide a reliable basis for tracking and detecting trends in high-performance computing and bases rankings on HPL, a portable organization's semiannual list of the 500 fastest computers usually includes many clusters. TOP500 is a collaboration between the University of Mannheim The University of Mannheim is one of the younger German universities. The University’s trademark is its distinct profile. This is characterized by Mannheim’s economic and social sciences which are closely intertwined with humanities, law, mathematics and computer science. The University of Mannheim offers a wide range of study programs, the University of Tennessee The University of Tennessee , sometimes called the University of Tennessee, Knoxville (UT Knoxville, or UTK) is a public land-grant university headquartered at Knoxville. Founded in 1794, it is the flagship institution of the statewide University of Tennessee system with nine undergraduate departments and eleven graduate departments and hosts, and the National Energy Research Scientific Computing Center at Lawrence Berkeley National Laboratory The Ernest Orlando Lawrence Berkeley National Laboratory , is a U.S. Department of Energy (DOE) national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus. It is managed and operated by the University of California. As of November 17, 2009, the top supercomputer A supercomputer is a computer that is at the frontline of current processing capacity, particularly speed of calculation. Supercomputers were introduced in the 1960s and were designed primarily by Seymour Cray at Control Data Corporation , which led the market into the 1970s until Cray left to form his own company, Cray Research. He then took over is the Department of Energy's The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material. Its responsibilities include the nation's nuclear weapons program, nuclear reactor production for the United States Navy, energy conservation, Jaguar system with performance of 1759 TFlops In computing, FLOPS is an acronym meaning FLoating point Operations Per Second. The FLOPS is a measure of a computer's performance, especially in fields of scientific calculations that make heavy use of floating point calculations, similar to the older, simpler, instructions per second. Since the final S stands for "second", conservative measured with the High-Performance LINPACK benchmark.

Clustering can provide significant performance benefits versus price. The System X supercomputer at Virginia Tech Virginia Polytechnic Institute and State University, better known as Virginia Tech, is a land grant polytechnic university in Blacksburg, Virginia, United States, the 28th most powerful supercomputer on Earth as of June 2006[2], is a 12.25 TFlops computer cluster of 1100 Apple Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh computers, the iPod, the iPhone and the iPad. Apple software includes the Mac OS X operating system; the iTunes media browser; the iLife suite XServe Xserve is the name of Apple's 1U rackmount line of server computers. When the Xserve was introduced in 2002, it was Apple's first designated server hardware design since the Apple Network Servers of 1996. It initially featured one or two PowerPC G4 processors, but was later switched over to the new PowerPC G5, and now runs on two quad-core Intel G5 The PowerPC 970, PowerPC 970FX, PowerPC 970GX, and PowerPC 970MP, are 64-bit Power Architecture processors from IBM introduced in 2002. When used in Apple Inc. machines, they were dubbed the PowerPC G5 2.3 GHz dual-processor machines (4 GB The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units (SI), therefore 1 gigabyte is 1000000000bytes. The unit symbol for the gigabyte is GB or Gbyte, but not Gb (lower case b) which is typically used for the gigabit RAM Random-access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order (i.e., at random). "Random" refers to the idea that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the, 80 GB SATA Serial ATA (Serial Advanced Technology Attachment) is a computer bus interface for connecting host bus adapters to mass storage devices such as hard disk drives and optical drives. Serial ATA was designed to replace the older ATA (AT Attachment) standard (also known as EIDE). It is able to use the same low level commands, but serial ATA host- HD A hard disk drive is a non-volatile storage device for digital data. It features one or more rotating rigid platters on a motor-driven spindle within a metal case. Data is encoded magnetically by read/write heads that float on a cushion of air above the platters, with modern storage capacity measured in gigabytes and terabytes) running Mac OS X Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, Mac OS X has been included with all new Macintosh computer systems. It is the successor to Mac OS 9, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 198 and using InfiniBand InfiniBand is a switched fabric communications link used in high-performance computing and enterprise data centers . Its features include high throughput, low latency, quality of service and failover, and it is designed to be scalable. The InfiniBand architecture specification defines a connection between processor nodes and high performance I/O interconnect. The cluster initially consisted of Power Mac G5s; the rack-mountable XServes are denser than desktop Macs, reducing the aggregate size of the cluster. The total cost of the previous Power Mac system was $5.2 million, a tenth of the cost of slower mainframe computer Mainframes are powerful computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing supercomputers. (The Power Mac G5s were sold off.)

The central concept of a Beowulf cluster is the use of commercial off-the-shelf Commercial, off-the-shelf or simply off the shelf (OTS, which may also include free software) computer software or hardware, technology, or computer products, are ready-made and available for sale, lease, or license to the general public. They are often used as alternatives to in-house developments or one-off government-funded developments. The (COTS) computers to produce a cost-effective alternative to a traditional supercomputer. One project that took this to an extreme was the Stone Soupercomputer.

However it is worth noting that FLOPs (floating point operations per second), aren't always the best metric for supercomputer speed. Clusters can have very high FLOPs, but they cannot access all data in the cluster as a whole has at once. Therefore clusters are excellent for parallel computation, but much poorer than traditional supercomputers at non-parallel computation.

JavaSpaces is a specification from Sun Microsystems Sun Microsystems, Inc. is a wholly owned subsidiary of Oracle Corporation, selling computers, computer components, computer software, and information technology services. Sun was founded on February 24, 1982. The company was headquartered in Santa Clara, California , on the former west campus of the Agnews Developmental Center that enables clustering computers via a distributed shared memory.

Consumer game consoles

Due to the increasing computing power of each generation of game consoles A video game console is an interactive entertainment computer or modified computer system that produces a video display signal which can be used with a display device to display a video game. The term "video game console" is used to distinguish a machine designed for consumers to buy and use solely for playing video games from a personal, a novel use has emerged where they are repurposed into HPC High-performance computing uses supercomputers and computer clusters to solve advanced computation problems. Today, computer systems approaching the teraflops-region are counted as HPC-computers clusters. Some examples of game console clusters are Sony PlayStation clusters and Microsoft Microsoft Corporation is a public multinational corporation based in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions. Established on April 4, 1975 to develop and sell BASIC interpreters for the Altair 8800, Xbox clusters. It has been suggested on a news website that countries which are restricted from buying supercomputing technologies may be obtaining game systems to build computer clusters for military use.[3]

History

The history of cluster computing is best captured by a footnote in Greg Pfister's In Search of Clusters: “Virtually every press release from DEC mentioning clusters says ‘DEC, who invented clusters…’. IBM did not invent them either. Customers invented clusters, as soon as they could not fit all their work on one computer, or needed a backup. The date of the first is unknown, but it would be surprising if it was not in the 1960s, or even late 1950s.”[4]

The formal engineering basis of cluster computing as a means of doing parallel work of any sort was arguably invented by Gene Amdahl of IBM International Business Machines (NYSE: IBM) is a multinational computer, technology and IT consulting corporation headquartered in Armonk, North Castle, New York, United States. IBM is the world's fourth largest technology company and the second most valuable by global brand (after Coca-Cola). IBM is one of the few information technology companies, who in 1967 published what has come to be regarded as the seminal paper on parallel processing: Amdahl's Law Amdahl's law, also known as Amdahl's argument, is named after computer architect Gene Amdahl, and is used to find the maximum expected improvement to an overall system when only part of the system is improved. It is often used in parallel computing to predict the theoretical maximum speedup using multiple processors. Amdahl's Law describes mathematically the speedup one can expect from parallelizing any given otherwise serially performed task on a parallel architecture. This article defined the engineering basis for both multiprocessor computing and cluster computing, where the primary differentiator is whether or not the interprocessor communications are supported "inside" the computer (on for example a customized internal communications bus or network) or "outside" the computer on a commodity network.

Consequently the history of early computer clusters is more or less directly tied into the history of early networks, as one of the primary motivation for the development of a network was to link computing resources, creating a de facto computer cluster. Packet switching Packet switching is a digital networking communications method that groups all transmitted data – irrespective of content, type, or structure – into suitably-sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network. When traversing network adapters, switches, routers and other networks were conceptually invented by the RAND RAND Corporation is a nonprofit global policy think tank first formed to offer research and analysis to the United States armed forces by Douglas Aircraft Company. It is currently financed by the U.S. government, a private endowment, corporations including the healthcare industry, universities and private individuals. The organization has long corporation in 1962. Using the concept of a packet switched network, the ARPANET ARPANET , created by a small research team at the head of the Massachusetts Institute of Technology and the Defense Advanced Research Projects Agency (DARPA) of the United States Department of Defense, was the world's first operational packet switching network, and the predecessor of the contemporary global Internet. The packet switching of the project succeeded in creating in 1969 what was arguably the world's first commodity-network based computer cluster by linking four different computer centers (each of which was something of a "cluster" in its own right, but probably not a commodity cluster). The ARPANET project grew into the Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and—which can be thought of as "the mother of all computer clusters" (as the union of nearly all of the compute resources, including clusters, that happen to be connected). It also established the paradigm in use by all computer clusters in the world today—the use of packet-switched networks to perform interprocessor communications between processor (sets) located in otherwise disconnected frames.

The development of customer-built and research clusters proceeded hand in hand with that of both networks and the Unix Unix is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit operating system from the early 1970s, as both TCP/IP The Internet Protocol Suite is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard. Today's IP networking and the Xerox PARC PARC , formerly Xerox PARC, is a research and co-development company in Palo Alto, California with a distinguished reputation for its contributions to information technology and hardware systems project created and formalized protocols for network-based communications. The Hydra operating system was built for a cluster of DEC PDP-11 The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corp. from 1970 into the 1990s. Though not explicitly conceived as a successor to DEC's PDP-8 computer in the PDP series of computers (both product lines lived in parallel for more than 10 years), the PDP-11 replaced the PDP-8 in many real-time applications. It had several minicomputers called C.mmp at Carnegie Mellon University Coordinates: 40°26′36″N 79°56′37″W / 40.443322°N 79.943583°W Carnegie Mellon University is a private research university in Pittsburgh, Pennsylvania. The university began as the Carnegie Technical Schools, founded by Andrew Carnegie in 1900. In 1912, the school became Carnegie Institute of Technology and began granting four-year in 1971. However, it was not until circa 1983 that the protocols and tools for easily doing remote job distribution and file sharing were defined (largely within the context of BSD Berkeley Software Distribution is the UNIX operating system derivative developed and distributed by the Computer Systems Research Group (CSRG) of the University of California, Berkeley, from 1977 to 1995 Unix, as implemented by Sun Microsystems) and hence became generally available commercially, along with a shared filesystem.

The first commercial clustering product was ARCnet, developed by Datapoint in 1977. ARCnet was not a commercial success and clustering per se did not really take off until DEC released their VAXcluster product in 1984 for the VAX/VMS operating system. The ARCnet and VAXcluster products not only supported parallel computing, but also shared file systems and peripheral devices. The idea was to provide the advantages of parallel processing, while maintaining data reliability and uniqueness. VAXcluster, now VMScluster, is still available on OpenVMS systems from HP running on Alpha and Itanium systems.

Two other noteworthy early commercial clusters were the Tandem Himalaya (a circa 1994 high-availability product) and the IBM S/390 Parallel Sysplex (also circa 1994, primarily for business use).

No history of commodity computer clusters would be complete without noting the pivotal role played by the development of Parallel Virtual Machine (PVM) software in 1989. This open source software based on TCP/IP communications enabled the instant creation of a virtual supercomputer—a high performance compute cluster—made out of any TCP/IP connected systems. Free form heterogeneous clusters built on top of this model rapidly achieved total throughput in FLOPS that greatly exceeded that available even with the most expensive "big iron" supercomputers. PVM and the advent of inexpensive networked PCs led, in 1993, to a NASA project to build supercomputers out of commodity clusters. In 1995 the invention of the "beowulf"-style cluster—a compute cluster built on top of a commodity network for the specific purpose of "being a supercomputer" capable of performing tightly coupled parallel HPC computations. This in turn spurred the independent development of Grid computing as a named entity, although Grid-style clustering had been around at least as long as the Unix operating system and the Arpanet, whether or not it, or the clusters that used it, were named.

Technologies

MPI is a widely-available communications library that enables parallel programs to be written in C, Fortran, Python, OCaml, and many other programming languages.

The GNU/Linux world supports various cluster software; for application clustering, there is Beowulf, distcc, and MPICH. Linux Virtual Server, Linux-HA - director-based clusters that allow incoming requests for services to be distributed across multiple cluster nodes. MOSIX, openMosix, Kerrighed, OpenSSI are full-blown clusters integrated into the kernel that provide for automatic process migration among homogeneous nodes. OpenSSI, openMosix and Kerrighed are single-system image implementations.

Microsoft Windows Compute Cluster Server 2003 based on the Windows Server platform provides pieces for High Performance Computing like the Job Scheduler, MSMPI library and management tools. NCSA's recently installed Lincoln is a cluster of 450 Dell PowerEdge 1855 blade servers running Windows Compute Cluster Server 2003. This cluster debuted at #130 on the Top500 list in June 2006.

gridMathematica provides distributed computations over clusters including data analysis, computer algebra and 3D visualization. It can make use of other technologies such as Altair PBS Professional, Microsoft Windows Compute Cluster Server, Platform LSF and Sun Grid Engine.[5]

gLite is a set of middleware technologies created by the Enabling Grids for E-sciencE (EGEE) project.

Another example of consumer game products being added to high-performance computing is the Nvidia Tesla workstation, which gets its processing power by harnessing the power of multiple graphics accelerator processor chips.

See also

References

  1. ^ Bader, David; Robert Pennington (June 1996). "Cluster Computing: Applications". Georgia Tech College of Computing. http://www.cc.gatech.edu/~bader/papers/ijhpca.html. Retrieved 2007-07-13.
  2. ^ TOP500 List - June 2006 (1-100) | TOP500 Supercomputing Sites
  3. ^ Farah, Joseph (2000-12-19). "Why Iraq's buying up Sony PlayStation 2s". World Net Daily. http://www.worldnetdaily.com/news/article.asp?ARTICLE_ID=21118.
  4. ^ Pfister, Gregory (1998). In Search of Clusters (2nd ed.). Upper Saddle River, NJ: Prentice Hall PTR. p. 36. ISBN 0-13-899709-8.
  5. ^ gridMathematica Cluster Integration.

Further reading

External links

Wikimedia Commons has media related to: Computer cluster
Parallel computing topics
General Cloud computing · High-performance computing · Cluster computing · Distributed computing · Grid computing
Parallelism (levels) Bit · Instruction · Data · Task
Threads Superthreading · Hyperthreading
Theory Amdahl's law · Gustafson's law · Cost efficiency · Karp-Flatt metric · slowdown · speedup
Elements Process · Thread · Fiber · PRAM
Coordination Multiprocessing · Multithreading · Memory coherency · Cache coherency · Barrier · Synchronization · Application checkpointing
Programming Models (Implicit parallelism · Explicit parallelism · Concurrency) · Flynn's taxonomy (SISD • SIMD • MISD • MIMD (SPMD))
Hardware

Multiprocessing (Symmetric · Asymmetric) · Memory (NUMA · COMA · distributed · shared · distributed shared) · SMT

MPP · Superscalar · Vector processor · Supercomputer · Beowulf
APIs POSIX Threads · OpenMP · PVM · MPI · UPC · Intel Threading Building Blocks · Boost.Thread · Global Arrays · Charm++ · Cilk · Co-array Fortran · CUDA · FastFlow
Problems Embarrassingly parallel · Grand Challenge · Software lockout · Scalability · Race conditions · Deadlock · Deterministic algorithm

Categories: Cluster computing | Parallel computing | Concurrent computing | Supercomputers | Local area networks | Classes of computers

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