1. Authors: David G. Andersen et al. Offense: Chang Seok Bae Yi Yang

2. Outline Limitations

3. The name Wimpy Nodes? "I worry no manufacturer will ever want to produce a device called a wimpy node," Andersen said. If somebody wants to commercialize it, they'd better think about changing the name.

4. FAWN-KV architecture FAWN clusters can handle roughly 350 key-value queries per Joule of energy-two orders of magnitude more than a disk-based system Flash is over two orders of magnitude more efficient than mechanical disks in terms of queries/Joule What is the contribution of FAWN-KV architecture?

5. Flash memory Basically, Flash memory is still expensive comparing disk Typical flash drive is $2 per gigabyte Flash memory drives have limited lifetimes (10e5 write cycles per cell)* Somehow unstable Asymmetric read vs. write performance causes problems** * Kerekes, Zsolt, “SSD Myths and Legends – “write endurance””, StorageSearch.com ** http://anandtech.com/storage/showdoc.aspx?i=3667&p=3

6. Workload Your solution has limitation on read-intensive, small object workloads Transactions Correct recovery form failure Isolation between programs accessing database concurrently

7. Workload (continued) Data store vs. database emphasize that data store does not provide transactional and relational interfaces. Such simple data lookup environments lack the complexities of more complex data processing workloads Do the same conclusions apply for complex data processing workloads?

8. Failure It’s critical, need to be well-addressed. Nodes are assumed to be fail-stop. How about the communication failure? The failure of a link or switch?

9. Power & Cost Two switches? Large cluster would require many more network switches, increasing the ratio of network power to FAWN node power. Increase network related hardware and power costs due to the need for more switches; human cost of management.

10. Power & Cost (continued) Processing power seems to be poor if it needs fast response times Workloads tend to be diverse and dynamic Sometimes I/O bounds but sometimes more computational

11. Migration issue How much effort should be made to use your suggestion in commodity distributed storage system Compatibility Cost Then, what about return of invest

12. Thank you