Network Load Balancing Setup and Configuration

The machines residing in the individual Network Load Balancing (NLB) configurations must be configured prior to K2 installation. The following deployment consideration sections discuss NLB setup

Network Load Balancing vs Clustering

NLB clusters dynamically distribute the flow of incoming TCP and UDP traffic among the cluster nodes according to a set of traffic-handling rules. NLB clusters provide a highly available and scalable platform for applications such as IIS. NLB is used for stateless applications; i.e. those that do not rely on any state as a result of a request.

NLB and server clusters complement each other in complex architectures: NLB is used for load balancing requests between front-end Web servers while server clusters provide high availability for backend database access.

A server cluster is a collection of servers that together provides a single, highly available platform for hosting applications. Applications can be failed-over to ensure high availability in the event of planned downtime due to maintenance or unplanned downtime due to hardware, Operating System or application failures. Server clusters provide a highly available platform for applications such as SQL Servers. Server clusters are used for stateful applications that rely on some state context from one request to the next.

Server clusters provide high availability and disaster tolerance for mission-critical database management, file sharing, intranet data sharing, messaging, and general business applications. With Windows Server 2008 R2 with SP1, failover clustering allows flexibility for adding and removing hardware in a geographically dispersed cluster environment, as well as providing improved scaling options for applications. Windows Server 2008 R2 also allows server clusters to be deployed in a variety of different configurations, in particular:

Single cluster configurations with dedicated storage.
Multiple clusters on a storage area network (SAN), potentially with other Windows servers or operating systems.

In a clustered environment, the K2 Server is only supported on NLB clusters. Installing the K2 Server in a Windows server cluster environment is not supported.

Physical Network Environment

Since a large installation typically uses more than one Web server in a load-balanced configuration, setting up the local network infrastructure can be more complex than setting up a normal Web application system. This is because the Windows NLB technology causes multiple Web servers to appear as a single server. As a result, the network infrastructure must support the creation of multiple broadcast domains (virtual local area network, or VLAN) to segment incoming Web requests from the main production network.

NLB broadcasts incoming traffic destined for the servers in an NLB group to all ports within their network collision domain (in this case, VLAN). In normal Web server deployment scenarios, the incoming traffic typically consists of a small number of HTTP GET requests and this may not be an issue. However, K2 blackpearl and SharePoint network traffic may consist of large documents moving between servers.

As a result, it is imperative that the NLB adapters for the Web servers are not connected to the normal server network. A separate logical or physical network, such as a VLAN, must be created so the larger amount of incoming traffic is not flooded to the network ports of other servers, thereby causing performance degradation on all servers within the network, not just the Web servers.

Furthermore, traffic to and from a SharePoint site or the K2 Workspace involves a considerable amount of communication from the Web servers to the back-end servers running SQL Server; good connectivity between them is required. It is therefore recommended that Web servers be dual-homed:

One network adapter handling the incoming Web requests by using NLB
One network adapter acting as a normal server adapter to communicate to the server running SQL Server along with the other servers within the infrastructure, such as domain controllers for authentication purposes

Installing Components in a Redundant Environment

When installing for load balancing, the installation must be performed on each machine independently. If for example the K2 Server is being installed in a NLB cluster similar to the example below, the server components must be installed on each individual machine.
The NLB cluster is configured using the operating system and should be configured prior to installing and configuring the K2 environment.
As illustrated below, when installing the components for load balancing, the components need to be pointed to the K2 Server NLB cluster. For example, the component is pointed at the NLB name and not the individual machines within the NLB cluster.

Additional Resources for NLB

NLB FAQ:
http://technet.microsoft.com/en-us/library/cc725691(v=WS.10).aspx

While infrastructure changes are required by K2, each environment is different and has its peculiarities which must be taken into account. Modifying the infrastructure could have unforeseen results if the changes are not appropriately understood or managed. Given the broad spectrum of underlying infrastructure utilized, it is recommended that a panel or committee with appropriate skill in each area concerned be assembled to outline the underlying infrastructure changes and gauge the impact of the required changes.