Windows Server 2003 R2 Datacenter Edition includes the features from Windows Server 2003 R2 Standard Edition and Windows Server 2003 R2 Enterprise Edition. It also offers the following extra features and capabilities: Expanded physical memory space. On both 64-bit architectures, Windows Server 2003 R2 Datacenter Edition supports up 2 TB of physical RAM in SP2 (1 TB in SP1). On 32-bit Intel platforms, Windows Server 2003 R2 Datacenter Edition supports Physical Address Extension (PAE), which extends system memory capability to 128 GB of physical RAM. Scale to up to 64 processors. Both 64-bit versions scales up to 64 processors. The x86/32-bit version scales up to 32 processors. Intel Hyper-Threading support. Intel Hyper-Threading Technology allows a single physical processor to execute multiple threads (instruction streams) simultaneously, potentially providing greater throughput and improved performance. Non-Uniform Memory Access (NUMA) support. System firmware can create a table called the Static Resource Affinity Table that describes the NUMA topology of the system. Windows Server 2003 Datacenter Edition uses this table to improve the efficiency of the operating system by applying NUMA awareness to application processes, default affinity settings, thread scheduling, and memory management. Cluster service. 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 2003 R2 Datacenter Edition, and Windows Server 2003 R2 Enterprise Edition, cluster service size has increased from four-node clusters to eight-node clusters. This provides increased flexibility for adding and removing hardware in a geographically dispersed cluster environment, as well as providing improved scaling options for applications. Windows Server 2003 R2 Datacenter Edition, 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. Direct access for SANs with Windows Sockets. Windows Sockets applications that use Transmission Control Protocol/Internet Protocol (TCP/IP) can now obtain the performance benefits of SANs without making application modifications. The fundamental component of this technology is a Windows Sockets layered service provider that emulates TCP/IP semantics over native SAN service providers. Terminal Services Session Directory. Terminal Services Session Directory is a load balancing feature that allows users to easily reconnect to a disconnected session on a server farm running Terminal Services. Session Directory is compatible with the Windows Server 2003 load balancing service, and is supported by third-party, external load balancer products. Windows System Resource Manager. In Windows Server 2003 Enterprise Edition, and Windows Server 2003, Datacenter Edition, the Windows System Resource Manager (WSRM) feature enables an administrator to allocate CPU and memory utilization on a per-application basis. This is a useful tool for server consolidation.