Every day internet gives new terminology that we might be not familiar with. Bottom line is that more and more we deal with web hosting, more we should be getting learning about the server's means and the server's processes that occur on day-to-day basis. Clustering and Network Load Balancing are the concepts that look very similar. But now, let's sort things out to have the straight idea of what these two concepts stand for.
Windows clustering gives three different, yet, complementary, clustering technologies. The clustering technologies use a number of products, but generally can be used combined or separately in order to provide scalable and highly-available services.
Network Load Balancing clusters give scalability and high-availability for TCP- and UDP-based services and applications by combining up to 32 servers running Windows Sever 2003, Web Edition and others. In the case of using Network Load Balancing to build a group of cloned/ identical clustered computers, you can enhance the availability of servers. They are Web and File Transfer (FTP) servers, ISA server (for proxy servers and firewall services), virtual private network (VPN) servers, Windows Media servers, Terminal Services over your corporate LAN. NLB clusters can be installed through Network Connections or by using the Network Load Balancing Manager.
Server clusters give high availability for applications through the failover of resources. Server clusters focus on preserving client access to applications and system services, such as Microsoft Exchange (messaging), SQL Server for database applications, and file/print services. By default, all clustering and administration software files are automatically installed on your computer with operating system of Windows Server 2003 family.
Also, there is Component Load Balancing clusters, a not commonly used method. Component Load Balancing clusters provide high scalability and availability by enabling COM+ applications (eCommerce web site shopping cart application) to be delivered between multiple servers. Component Load Balancing clusters is a feature of Microsoft Application Center 2000 in Microsoft TechNet.
Network Load and Clustering apply only to servers sharing the same services. Having a front-end/ back end topology serves for security and easing the load to a lesser extent.
Network Load Balancing (NLB) and the Cluster service apply to the Network Load Balancing Manager that offers these two services. Let's give definitions to both these concepts.
The Network Load Balancing service gives means for load balancing TCP/IP traffic between multiple servers in specific NLB cluster. The servers that participate in the NLB cluster do not share storage or any other resources. These NLB cluster servers run their own instances of the load-balancing applications. NLB simply manages the incoming traffic. NLB balances it out to the servers participating in that particular cluster. Yet, NLB provides no failover capability.
On the other hand, servers that participate in the Cluster Service does provide redundancy and failover capability. Cluster Service Servers generally share common storage and function as a single, logical unit.
By contrast NLB cluster is a group of individual servers working independently to process the traffic that the NLB service gives them. Essentially, the NLB service enables all servers in the NLB cluster to be addressed by a single IP address.
Clustering is used to store more information, store it redundantly, provides more horsepower and others. NLB would be used more commonly to provide serves less inundated tons of requests.
Clustering is commonly used by back-end servers as Network Load Balancing is preferred for front-end serves. When a back-end mailbox store goes offline, the information hosted there needs to be shifted to another server which is outside the scope of NLB. Having a front-end/ back-end topology would allow putting a front-end server in your network perimeter. It will lock down access to it from the outside world (no RPC), having an internal back-end server that stores the mailboxes and in general all real data.
An expert can combine NLB clustering with Cluster Service clusters, but these two cluster types must remain separate because the server cannot participate in both types of clusters. The best way is using of common solution is to build an NLB cluster upstream to service a Cluster Service cluster.
Finishing up the overview, we can say that Clustering is proprietary to the server's application, yet NLB clustering is able to provide services for any and all applications or web servers.
