Building Fault-Tolerant Windows Server 2008 R2 Systems - Designing Fault-Tolerant IP Networks

Network design can also incorporate fault tolerance by creating redundant network routes and by utilizing technologies that can group devices together for the purposes of load balancing and device failover. Load balancing is the process of spreading requests across multiple devices to keep individual device load at an acceptable level. Failover is the process of moving services offered on one device to another upon device failure, to maintain availability. Common scenarios for creating fault-tolerant IP networks can include, but are not limited to, the following:

» Acquiring multiple network connections between the data center and the Internet—This includes using different Internet service providers and, hopefully, each of the connections is not connected to the same external telco box on the street as this becomes the single point of failure if hit by a car, truck, or cut off from communications.

» Deploying multiple and redundant firewalls, virtual private networks (VPNs), and network routers that will failover to one another—This usually involves software or hardware configurations that allow each of the devices to communicate with one another to detect failures. These devices, when deployed in redundant configurations, can be leveraged in an active/passive configuration where only a single primary device is used and the secondary device only comes online when the primary fails. Alternatively, in many cases these devices can be used in an active/active configuration that disperses or distributes the load and requests across each device and when a single device fails, the remaining device handles the entire load.

» Deploying critical servers with multiple network adapters connected to separate network switches—This allows a server to be connected and available on different switches in case a single network card in the server fails or if the port or the entire network switch or blade fails.

» Deploying hardware-based NLB devices—Many network switches, routers, and certain devices created just for this purpose can provide some, if not all, of the functionality included in Windows Server 2008 R2 NLB. This, of course, might be the best choice for load balancing at the network level when organizations deploy and support systems other than Windows Server 2008 R2 and when they also need to load-balance network devices, such as firewalls and VPN devices.

» Deploying servers with multiple network adapters using third-party network teaming software—This configuration uses third-party software installed and configured on a server to create a new virtual network adapter that is used to provide access to the server system through a single or all of the physical network adapters on the server that are part of this configuration. Windows Server 2008 R2 supports teamed network adapters as long as the drivers and software are certified to work with Windows Server 2008 R2.

If the Windows Server 2008 R2 system utilizes iSCSI storage, the network adapters designated for iSCSI communications are not supported on teamed network adapters.

Source of Information : Sams - Windows Server 2008 R2 Unleashed (2010)