One of the most widely used distributed applications are distributed file systems that allows sharing of files on an intranet. Today's networks allows for the construction of distributed file systems that outperforms local file systems. However, this performance comes at a price, namely that one cannot have to one-copy semantics from local file systems. In this lecture, we take a look at the general construction of distributed file systems, followed by a case study of two different implementations that qua their different design goals adopt different semantic models for the file system.

[DS] Chapter 8.

• [DS] 8.1, 8.5, 8.7, 8.11, 8.12, 8.15, 8.16, 8.17
• Consider a company Z  who has one main branch and a number of very small offices situated around the globe. Z has its company information stored in a well-protected, secured, backedup file server at the main office. The smaller branches have internet access via connections of similar quality and performance like ADSL.

• • Discuss how to design a distributed file system targeted for Z! How will you arrange caching and consistency of files?
  • What issues are different in this situation compared a file system for a LAN or campus environment?