Введение
Термин cluster
в основном используется для описания распределенной вычислительной системы.
Gregory Pfister в своей книге от 1997 года,
В поисках кластера,[1]
около 500 страниц посвятил описанию этой проблемы.
Он дал следующее определение :
Кластер - это такой тип параллельной вычислительной системы,который :
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Состоит из набора компьютеров , связанных друг с другом через общий коннект.
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Используется как единый универсальный компьютерный ресурс.
В дальнейшем я буду использовать термин Linux Enterprise Cluster
для описания его свойств и архитектуры.
Properties of a Linux Enterprise Cluster
If we succeed in building a system that can be used as a "single unified computing resource" using "a local computing system comprising a set of independent computers and a network interconnecting them," then the user, the programmer, the program, and even the networking equipment and the other servers on the network will not know that they are using or communicating with a cluster.
Thus, the four basic properties of a Linux Enterprise Cluster are:
Users do not know that they are using a cluster
Nodes within a cluster do not know they are part of a cluster
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In other words, the operating system does not need to be modified to run on a cluster node, and the failure of one node in the cluster has no effect on the other nodes inside the cluster. (Each cluster node is whole or complete—it can be rebooted or removed from the cluster without affecting the other nodes.)
A Linux Enterprise Cluster is a commodity cluster because it uses little or no specialty hardware and can use the normal Linux operating system. Besides lowering the cost of the cluster, this has the added benefit that the system administrator will not have to learn an entirely new set of skills to provide basic services required for normal operation, such as account authentication, host-name resolution, and email messaging.
Applications running in the cluster do not know that they are running inside a cluster
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If an application—especially a mission-critical legacy application—must be modified to run inside the cluster, then the application is no longer using the cluster as a single unified computing resource.
Some applications can be written using a cluster-aware application programming interface (API),[2] a Message Passing Interface (MPI),[3] or distributed objects. They will retain some, but not all, of the benefits of using the cluster as a single unified computing resource. But multiuser programs should not have to be rewritten[4] to run inside a cluster if the cluster is a single unified computing resource.
Other servers on the network do not know that they are servicing a cluster node
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The nodes within the Linux Enterprise Cluster must be able to make requests of servers on the network just like any other ordinary client computer. The servers on the network (DNS, email, user authentication, and so on) should not have to be rewritten to support the requests coming from the cluster nodes.
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