A: Server 2008 and Server 2008 R2 include support for four network accelerations that specifically benefit iSCSI connections. These accelerations require participation from hardware components, so verify support from your manufacturers. When they're supported, each increases the performance of iSCSI connections.
TCP Chimney Offload transfers TCP/IP protocol processing from the server's CPU to the chipset on the network adapter. This feature sometimes requires separate licensing from the network adapter manufacturer.
Virtual machine queue distributes received network frames into different queues based on the target virtual machine (VM). It uses hardware packet filtering to reduce the overhead of routing network packets to VMs. This distribution allows different CPUs to process the incoming data. VMQ must be supported by network adapters, and is commonly associated with Intel NICs and processors.
Receive side scaling distributes the load from network adapters across multiple CPUs. It was first available in Windows Server 2008 RTM, with R2 adding improved initialization and CPU selection at startup.
NetDMA is the final acceleration. This feature offloads the network subsystem memory copy operation to a dedicated engine to improve performance.
