Windows Server 2003 includes a number of applications and services that can be clustered using either the Cluster Service or NLB. They are as follows:
Internet Information Services (IIS)? Supported by both the Cluster Service and NLB. Using NLB makes the most sense because you can have up to 32 independent servers in an NLB cluster. NLB provides both failover and load balancing, whereas the Cluster Service can provide only failover.
DHCP Service? Supportedonly by the Cluster Service.
Distributed file system (DFS) roots? Even though NLB could technically load balance between DFS roots, there's usually little need to do so. The Cluster Service provides failover for the DFS root, which is what enterprises are usually interested in.
Distributed Transaction Coordinator? Supported only by the Cluster Service.
File shares? Technically, you could provide load balancing of file servers by using NLB. However, it's unsafe to do so because no provision exists for synchronizing copies for changes and so forth. The Cluster Service provides failover for file shares, and DFS allows you to load balance and synchronize file shares across multiple servers.
Message Queuing? Supportedonly by the Cluster Service.
Printer spools? Supported only by the Cluster Service. Theoretically, you could use NLB to provide load balancing between identical print queues on separate servers, but the queues would still be competing for the same physical print devices, so there would be little point in doing so.
Volume Shadow Copy Service Tasks? Supported only by the Cluster Service.
WINS Service (WINS)? Supported by the Cluster Service. You could potentially use NLB to provide load balancing between WINS servers, provided the servers were configured as replication partners. However, WINS typically isn't used so heavily that load balancing would be useful.
Of course, NLB can potentially support any TCP/IP-based application, and the Cluster Service can support TCP/IP-based applications that meet certain requirements. For more details, consult Windows Server 2003's online Help and Support Center.
For more information on DHCP, DFS, file sharing, print sharing, and WINS, see Chapter 8, "Network Services," p. 125.
For more information on IIS, see Chapter 7, "Internet Information Services," p. 101.