Understanding Threaded and Hybrid MPMs

Threads are similar to processes, but they can share memory and data with other threads. This has the advantage that there is no context switching (threads are part of the same process), and the disadvantage that poorly written code can take the whole server down with it. This can happen because a misbehaving thread is able to overwrite and corrupt data and code that belongs to other threads.

The Apache MPM for the Windows platform is an example of a threaded server MPM. Both threaded and process-based servers have their own sets of advantages and disadvantages. The Apache developers created a threaded MPM named Worker MPM that allows for a mixed approach. A server can spawn different processes, each one of them containing a number of threads.