Understanding Microsoft Cluster Service (MCCS) Clustering for SharePoint s SQL Database

Understanding Microsoft Cluster Service (MCCS) Clustering for SharePoint's SQL Database

Windows Server 2003 and SQL Server 2000 Enterprise support the shared-nothing cluster model. In a shared-nothing cluster each node of the cluster owns and manages its local resources and provides nonsharing data services. In case of a node failure, the disks and services running on the failed node fail over to a surviving node in the cluster. However, with high availability clustering, only one node is managing one particular set of disks and services at any given time.

SQL 2000 on Windows Server 2003 Enterprise can support up to four cluster nodes, whereas Windows Server 2003 Datacenter Edition can support up to eight nodes within a single cluster. Failover clustering of SQL Server 2000 can be configured in two ways: A single-instance failover (active/passive) configuration or a multiple-instance failover (active/active) configuration.

Single-Instance Failover Configuration

In a SQL Server single-instance failover configuration the cluster runs a single instance of SQL Server on all nodes in the cluster. If the main SharePoint SQL Server instance fails on the primary node, the surviving node or nodes will run the same SQL Server instance. In this configuration, all the servers within a cluster share a master database along with a set of SharePoint databases, such as the configuration and content databases.

Multiple-Instance Failover Configuration

In the multiple-instance failover configuration each of the active nodes has its own instance of SQL Server. Each instance of SQL Server includes a separate installation of the full service and can be managed, upgraded, and stopped independently. To apply a multiple-instance failover configuration, at least two instances of SQL Server must be installed on the cluster, and each instance should be configured to run on a certain node as its primary server.

SharePoint databases that regularly refer to each other should be placed on the same SQL Server instance. Before implementing a multiple-instance failover configuration, the expected load on each of the database applications should first be evaluated and followed by a second evaluation to determine whether a single node can handle can handle the combined load in a failover situation. If a single node cannot work, the use of two single-instance failover mode clusters should be considered.

NOTE

SharePoint databases will not be statically load balanced across multiple instances of SQL Server. This design alternative is best suited for organizations that have independent databases that could benefit from multiple servers being used at the same time, such as multiple site and content databases.