Advanced Distributed Systems (ADS) - naming and file systems

I'm taking a Advanced Distributed Systems course. We read papers and we present and discuss them.

The first two topics were:

Naming


1 - The Design and Implementation of an Intentional Naming System. William Adjie-Winoto, Elliot Schwartz, Hari Balakrishnan, Jeremy Lilley, SOSP 1999.
2 - Locating Objects in Wide-Area Systems. Maarten van Steen, Franz J. Hauck, Philip Homburg, Andrew S. Tanenbaum, IEEE Communications Magazine 36(1), January 1998, pages 104–109

Adjie-Winoto99 is a seminal paper for DHTs (Distributed Hash Tables). DHTs are good for matching items using identifiers but are not so good in matching attribute value ranges.

Another interesting topic were the trade-offs between soft-state (time limited persistence, fate sharing) and hard-state (persistence until explicit deletion). Hard requires recovery, checkpoints, transactions, logs. Soft allows for much faster node recovery.


Distributed File Systems

1 - An application of a context-aware file system. Christopher K. Hess, Roy H. Campbel. Springer-Verlag, London, 2003
2- The Google File System. Sanjay Ghemawat, Howard Gobioff, Shun-Tak Leung, SOSP 2003.

There are subtle differences in consistency definitions. For instance, the Google File System uses consistent and defined.

A file region is consistent if all clients will always see the same data, regardless of which replicas they read from.

A region is defined after a file data mutation if it is consistent and clients will see what the mutation writes in its entirety.

e.g. "The sky is yellow" - it's wrong, but it's consistent if everyone sees the same statement. Consistent isn't the same as correct.