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Improving Web Server Performance
Due to the cost of network processing, high-end Web servers in the near future will be unable to handle the continually increasing demand of more clients ever hungrier for more content. In fact, it is already commonplace today to use multiple servers to host a single Web site. Solutions such as multi-core systems or TCP Offload Engines have provided some relief, but are limited approaches because of the way they deal with memory.
However, a technique known as Remote Direct Memory Access (RDMA) has the capability to fully saturate high-speed networks while leaving the CPU free to do other tasks. RDMA not only moves the protocol processing to the network adapter, but also moves data directly from user space. This eliminates the need for costly memory copies.
While RDMA has proved successful in the high performance computing realm, it is not used widely because of compatibility issues with existing network infrastructures. But a new adaptation of RDMA called iWARP enables RDMA over ordinary TCP/IP-based networks. (See the iWARP below for more details.)
Leveraging iWARP, the research team at the Ohio Supercomputer Center has created a module (mod_rdma) that enables the popular Apache Web server to use RDMA to send and receive client data.
“In our study, we have outfitted a Web server with 10 gigabit iWARP hardware and used client-machines running iWARP-software modified wget and Apache bench programs,” said Dennis Dalessandro, networking researcher for OSC. “The result improves Web server performance, both in throughput and client request rate.”