A cluster is a group of servers and other resources that act like a single system and enable high availability and, in some cases, load balancing and parallel processing.or
A cluster consists of two or more computers working together to provide a higher level of availability, reliability, and scalability than can be obtained by using a single computer.
A cluster consists of two or more computers working together to provide a higher level of availability, reliability, and scalability than can be obtained by using a single computer.
When a failure occurs on one computer in a cluster, resources are redirected and the workload is redistributed to another computer in the cluster. You can use server clusters to ensure that users have constant access to important server-based resources.
Types of Server Clusters
There are three types of server clusters, based on how the cluster systems, called nodes, are connected to the devices that store the cluster configuration and state data.The sections that follow describe the three different types of server clusters:
- Single quorum device cluster, also called a standard quorum cluster
- Majority node set cluster
- Local quorum cluster, also called a single node cluster
Single Quorum Device Cluster
The most widely used cluster type is the single quorum device cluster, also called the standard quorum cluster. In this type of cluster there are multiple nodes with one or more cluster disk arrays, also called the cluster storage, and a connection device, that is, a bus. Each disk in the array is owned and managed by only one server at a time. The disk array also contains the quorum resource. The following figure illustrates a single quorum device cluster with one cluster disk array.
Single Quorum Device Cluster
Because single quorum device clusters are the most widely used cluster, this Technical Reference focuses on this type of cluster.
Single Quorum Device Cluster
Because single quorum device clusters are the most widely used cluster, this Technical Reference focuses on this type of cluster.Majority Node Set Cluster
Windows Server 2003 supports another type of cluster, the majority node set cluster. In a majority node set cluster, each node maintains its own copy of the cluster configuration data. The quorum resource keeps configuration data consistent across the nodes. For this reason, majority node set clusters can be used for geographically dispersed clusters. Another advantage of majority node set clusters is that a quorum disk can be taken offline for maintenance and the cluster as a whole will continue to operate.
The major difference between majority node set clusters and single quorum device clusters is that single quorum device clusters can operate with just one node, but majority node set clusters need to have a majority of the cluster nodes available for the server cluster to operate. The following figure illustrates a majority node set cluster. For the cluster in the figure to continue to operate, two of the three cluster nodes (a majority) must be available.
Majority Node Set Cluster
This Technical Reference focuses on the single quorum device cluster.
The major difference between majority node set clusters and single quorum device clusters is that single quorum device clusters can operate with just one node, but majority node set clusters need to have a majority of the cluster nodes available for the server cluster to operate. The following figure illustrates a majority node set cluster. For the cluster in the figure to continue to operate, two of the three cluster nodes (a majority) must be available.
Majority Node Set Cluster
This Technical Reference focuses on the single quorum device cluster.Local Quorum Cluster
A local quorum cluster, also called a single node cluster, has a single node and is often used for testing. The following figure illustrates a local quorum cluster.Local Quorum Cluster
