Read up on this article.
Learn more about direct I/O, concurrent I/O, asynchronous I/O, and best practices for each method of I/O implementation. This three-part series on the AIXÂ® disk and I/O subsystem focuses on the challenges of optimizing disk I/O performance. While disk tuning is arguably less exciting than CPU or memory tuning, it is a crucial component in optimizing server performance. In fact, partly because disk I/O is your weakest subsystem link, you can do more to improve disk I/O performance than on any other subsystem.
Credits go to “Ken Milberg” on writing the article. I enjoyed reading it, as it was very interesting.