Adapter-based vs. host-based processing
There are two basic ways to handle protocol processing, and the choice can make a huge difference in overall fabric performance, particularly as a cluster scales. Some vendors rely heavily on adapter-based ('on-load) processing techniques, in which each InfiniBand host channel adapter (HCA) includes an embedded microprocessor that processes the communications protocols. Other vendors primarily use host-based processing, in which the server processes the communications protocols. In the early days of InfiniBand clusters, a typical server may have had just one or two single- or dual-core processors. With the ability to issue one instruction per second at a relatively low clock rate, these servers benefitted from having communications processing offloaded to the host channel adapter.
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