The file system is a critically important part of any computing environment. This statement is particularly true for large, complex environments such as electronic commerce, Internet sites, electronic mail systems, highspeed computing systems, and On Line Transaction Processing systems (OLTP). For any such system, data more than any other single factor drive its sizing and configuration. The purpose of this book is to assist readers to make their Tru64 system perform at its best.

In this chapter, we cover some introductory topics in file systems. In the first two sections, we discuss the "what" and the "why" for this book to give readers an understanding of why such a book is absolutely essential in today's complex environments. Then, we acknowledge that we use a lot of jargon on this journey toward optimal file systems performance, so we attempt to remove as much of the ambiguity in terminology as possible. Finally, we enter some introductory topics in file system administration from the user's perspective. We conclude with a discussion of the often misunderstood topic of discretionary access controls and access control lists.