Tradeoffs in Designing Web Clusters
Tradeoffs in Designing Web Clusters
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DOI：
10.1109/mic.2002.1036041
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发表时间：
2002-09
期刊：
影响因子：
--
通讯作者：
D. Menascé
中科院分区：
文献类型：
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作者：
D. Menascé
大容量网站通常使用服务器集群来支持其体系结构。这些集群前面的负载均衡器将请求定向到各个服务器，其方式是尽可能均衡每个服务器上的负载。扩展Web集群有两种基本方法：添加更多相同类型的服务器(向外扩展，或水平扩展)或升级集群中服务器的容量(向上扩展，或垂直扩展)。虽然需要更详细和更复杂的模型来获得关于这类系统行为的更准确的结果，但简单排队理论提供了一个合理的抽象水平，以揭示在不同场景中使用哪种缩放方法。Web集群设计中的典型问题包括：是使用大量低容量廉价服务器还是使用少量高容量昂贵服务器来提供给定的性能水平；在给定的成本下需要多少台给定类型的服务器来提供一定的性能水平；以及需要多少台服务器来构建具有给定可靠性的Web站点。使用排队论，我研究了设计Web服务器集群所涉及的平均响应时间、容量、成本和可靠性权衡。
High-volume Web sites often use clusters of servers to support their architectures. A load balancer in front of such clusters directs requests to the various servers in a way that equalizes, as much as possible, the load placed on each. There are two basic approaches to scaling Web clusters: adding more servers of the same type (scaling out, or horizontally) or upgrading the capacity of the servers in the cluster (scaling up, or vertically). Although more detailed and complex models would be required to obtain more accurate results about such systems' behavior, simple queuing theory provides a reasonable abstraction level to shed some insight on which scaling approach to employ in various scenarios. Typical issues in Web cluster design include: whether to use a large number of low-capacity inexpensive servers or a small number of high-capacity costly servers to provide a given performance level; how many servers of a given type are required to provide a certain performance level at a given cost; and how many servers are needed to build a Web site with a given reliability. Using queuing theory, I examine the average response time, capacity, cost, and reliability tradeoffs involved in designing Web server clusters.