主题：【分享】Paper Summary

4. What is the authors' approach or solution?

  The authors solution includes:
  - Object-based storage devices
  - A globally known mapping function for locating file data
    (instead of object lists)
  - A scalable metadata manager that dynamically redelegates authority
    for directory subtrees based on load
  - A distributed autonomous system for managing the object stores

5. Why is it better than the other approaches or solutions?

  It scales to petabytes, provides nearly linear performance improvements
  as storage devices are added, degrades gracefully as storage devices are
  removed, and provides very high performance.

6. How did they test their solution?

  They ran parts of the storage system and observed their performance
  under various workloads. Data performance was tested on a single object
  store and on several object stores. Metadata performance was tested on
  a large cluster.

7. How does it perform?

  Performance is very good. The system appears to achieve its goals,
  although scalability could be improved in certain scenarios where a lot
  of sharing occurs.

8. Why is this work important?

  This work is important because storage systems continue to grow in size
  and data is becoming increasingly important.

3+ comments/questions

  * Why didn't they directly compare the performance of their system against
    that of any other storage systems?

  * What happens if you scale to exabytes? Will the system still work? What
    factors will limit its ability to scale further?

  * How much of the improvement is due to CRUSH, and how much to the design
    of the other parts of the system? Why didn't they do any tests to isolate
    the benefits of the individual design decisions?