Chapter Summary

This chapter has given you a broad overview of many aspects of computer input/output and storage systems. You have learned that different classes of machines require different I/O architectures. Large systems store and access data in ways that are fundamentally different from the methods used by smaller computers.

This chapter has illustrated how data is stored on a variety of media, including magnetic tape, disk, and optical media. Your understanding of magnetic disk operations will be particularly useful to you if you are ever in a position to analyze disk performance within the context of programming, system design, or problem diagnosis.

Our discussion of RAID systems should help you to understand how RAID can provide both improved performance and increased availability for systems upon which we all depend.

You have also seen a few of the ways in which data can be compressed. Data compression can help economize on disk and tape usage as well as reduce transmission time in data communications. An understanding of the specifics of these compression methods will help you to select the best method for a particular application. Our brief introduction to the ideas of information theory may help to prepare you for further work in computer science.

We hope that throughout our discussions, you have gained an appreciation for the tradeoffs that are involved with virtually every system decision. You have seen how we must often make choices between "better" and "faster," and "faster" and "cheaper" in so many of the areas that we have just studied. As you assume leadership in systems projects, you must be certain that your customers understand these tradeoffs as well. Often you need the tact of a diplomat to thoroughly convince your clients that there is no such thing as a free lunch.