CS262B Reading Summary

Scale and Performance in a Distributed File System

Joh H. Howard et al.

Summary by Feng Zhou
2/4/2004

Strong points of the paper are:

1. Introducing callbacks into Venus greatly reduces cache-validation messages and thus increases overall performance.  This exploits locaility in file access patterns of most programs, and write-sharing of files being a rare case.  On the downside callbacks increase complexity, and how the system will behave when network partition happens is not discussed.  According to the available description, the system will probably lose consistency in the presence of partition, because the client not able to receive call-backs from the server will assume the file is up-to-date.
2. Doing name-to-inode translation on the client side also increases performance, although this requires changes to the server and client system call interface.  This is quite similar to how directories are handled in NFS.  What the server knows is only files with unique ids ('fid' for AFS), but not directory structures.
3. The evaluation is done thoroughly, with a comprehensive benchmark suite.  And the motivation of the new design is shown by presenting benchmark results and analysis of a previous version.
   

The "scalability" measured throughout the evaluation part is actually raw performance.  Scalability normally should refer to the capacity of a system with regard to the amount of resource available.