Clusters vs. Grids

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There are many differences between Grid and Clusters. The following table shows comparison of Grid and Clusters.

Table 2.2: Comparison between Clusters and Grid

Grid represents a bigger framework and architecture, and focuses on the broader scope or objective. Grid incorporates many varied computing resources and the clusters often become one of the many components. A Grid enables the sharing, selection, and aggregation of a wide variety of geographically distributed resources including supercomputers, storage systems, data sources, and specialized devices owned by different organizations for solving large-scale resource intensive problems in science, engineering, and commerce. Clusters, on the other hand, focus on a specific objective and purpose, such as a database service or a web logic application server. These clusters fit into grid architecture very well for ultimate sharing of resources at a higher level of aggregation.

With technological advances it may not be long before a large number of nodes (say, 50 to 100 nodes) form a database cluster incorporating a variety of data stores consolidated into a huge data source. That may lead to a true Data Grid of different stores supported in a single large cluster.

Cluster Objectives

Traditionally, the term cluster was used to represent Server Clusters. Clustered systems are synonymous with a group of servers. The server, being the main layer or platform where the database or application service resides, is the most important component in providing availability and high performance.

 Clusters, with multiple nodes, primarily aim at protecting server availability. Any failure in a server is transparent to end-users and is hidden by the failover of the application or database to a surviving node. End users or clients have access to the surviving node, thus allowing processing to continue. In another situation, a group of nodes are joined together to provide database services, as in a parallel database. Failure of a single node does not interrupt access to the database since the secondary nodes are still active in providing database access.

Thus, the cluster technology focuses on providing an alternative to a failed server. However, we have to realize that there are many other layers or components, each of which is significant in maintaining overall availability of the database or application service. Although the server (node) is a very crucial component and plays the key role in running the database or application, there are other components, such as the disk storage units and networking equipment for which alternatives or backups need to be provided to meet the failure conditions. The traditional concept of clustering revolves around server clustering only.

With this in mind, administrators and managers should provide adequate redundancy for other components in order to have an effective high availability environment.