Failover Clustering

The cluster quorum contains the configuration settings for the entire cluster. With Windows Server 2008 R2, you can configure a cluster so that the quorum resource is not a single point of failure by using the majority node set or a hybrid of the majority node set and the quorum resource model. The cluster service can also isolate DLLs that perform actions incorrectly to minimize impact to the cluster, as well as verify consistency among copies of the quorum resource.

Administrators have better control and can achieve better performance with storage than was possible in previous releases. Failover clusters now support GUID partition table (GPT) disks that can have capacities of larger than 2 terabytes, for increased disk size and robustness. Administrators can now modify resource dependencies while resources are online, which means they can make an additional disk available without interrupting access to the application that will use it. And administrators can run tools in Maintenance Mode to check, fix, back up, or restore disks more easily and with less disruption to the cluster.

Networking has been enhanced to support Internet Protocol version 6 (IPv6) as well as Domain Name System (DNS) for name resolution, removing the requirement to have WINS and NetBIOS name broadcasts. Other network improvements include managing dependencies between network names and IP addresses: If either of the IP addresses associated with a network name is available, the network name will remain available. Because of the architecture of Cluster Shared Volumes (CSV), there is improved cluster node connectivity fault tolerance that directly affects Virtual Machines running on the cluster. The CSV architecture implements a mechanism, known as dynamic I/O redirection, in which I/O can be rerouted within the failover cluster based on connection availability.

Internet Protocol security (IPsec) can be used between clients and the cluster nodes, as well as between nodes so that you can authenticate and encrypt the data. Access to the cluster can also be audited to determine who connected to the cluster and when.

Increased Availability for Virtual Data Centers

One of the most important aspects of any data center is providing the highest possible availability for systems and applications. Virtual data centers are no exception to the need for consolidation, high availability, and, most of all, sophisticated management tools.

Hyper-V in Windows Server 2008 R2 includes the Live Migration feature, which allows you to move a virtual machine between two virtualization host servers without any interruption of service. The users connected to the virtual machine being moved might notice only a slight slowing in performance for a few moments. Otherwise, they will be unaware that the virtual machine was moved from one physical computer to another.

Live Migration Support Through Cluster Shared Volumes

Live Migration uses the new Cluster Shared Volumes (CSV) feature within Failover Clustering in Windows Server 2008 R2. The CSV volumes enable multiple nodes in the same failover cluster to concurrently access the same logical unit number (LUN).

While CSVs are currently employed mainly for Live Migration, their benefits will extend beyond that single scenario. For one, they’re easy to configure using simple NTFS rather than some other proprietary format. That means administrators won’t have to reformat their SANs to take advantage of CSVs. It also means administrators will have an easier time showing users only a single data repository rather than a small forest of silos—no more drive letter metaphors for end-users, just convenient networked storage. And last, CSVs don’t require config and management tools of their own. Windows Server administrators used to the tools in Windows Server 2008 can continue using those same consoles and they’ll simply work with CSVs in R2.