Improvement in Clustering Technology in Windows Server 2003
Many servers work together in a group like one computer is called a cluster. Clusters used to balance the load across two or more computers (performance reason) or to provide failover if one computer fails (fault tolerance reasons). Server 2003 supports two types of clustering: MS Cluster Service (MSCS) and Network Load Balancing (NLB).
Microsoft Cluster Service
Microsoft Cluster Service uses two or more physically connected servers, Microsoft called them nodes, which communicate with each other constantly. If one node detects that another’s status is offline, then it will take over the services provided by the offline node. Although, this happens behind the scenes and end-users are unaware of the process. Clustering service mostly used with mail servers, db servers and file and print servers. MSCS is supported in Enterprise Edition and Datacenter Edition of Windows 2003 Family. Server 2003 clustering includes the following new features compare with Windows 2000:
Network Load Balancing (NLB)
NLB nodes offer services at the same time. It can be accessed by the virtual name and whichever server is least busy can also respond the request. If one server goes offline, there is no transferring of services because all servers offer the services already. When a server goes offline, it is removed from the rotation of servicing requests until it comes back online. NLB is generally used with Web servers, application servers, terminal servers, and streaming media servers. NLB Manager is first time used Windows Server 2003.
Server 2003 includes a variety of features of NLB. it also can supports multiple network NICs and allow a single server to host different NLB clusters. We can use virtual clusters to set up multiple port rules for each cluster IP address, so each IP represents a different resource (Web page, application, and so forth). IGMP supports when NLB is configured in multicast mode. Using IGMP limits cluster traffic on the switch to the ports that have NLB server connected to them. This helps prevent switch flooding. (Switch flooding occurs when every server in an NLB cluster sees every packet addressed to the cluster.) it also can supports IPSec traffic.
Written by: Fahad Bin Ali KhilGi