1. Adaptive Load Sharing for Clustered Digital Library Servers Song, yong-joo System Software Lab, EECS, KAIST 9. 13, 2000

2. Contents Introduction Previous Work Clustered ADL server design Load sharing strategy Policy for node selection & load collection Experiment Conclusion & Critique

3. 3 Introduction Alexandria digital library Geographically-referenced materials Map, satellite image, digitized aerial photograph Large data Require extensive processing Goal : minimize response time

4. 4 Introduction(cont ’ d) Basic ADL Clustered ADL

5. 5

6. 6 Previous Work Clustered Web server design DNS round-robin rotation Problem : load imbalance SWEB Redirecting request by dynamic system load prediction of response time

7. 7 SWEB DNS round-robin rotation Redirect request to minimum expected response time server CPU, I/O load monitoring prediction of DB searching time load information update overhead

8. 8 Load Sharing strategy Class of request Text & image ( CPU & I/O usage small ) DB search ( CPU & I/O usage maybe large ) Image processing ( predictable ) Relative Server-site Response Cost Availability relative to the unloaded base node redirection threshold value

9. 9 Policy for load collection Broadcast – redundant info, load explosion Random poll – synchronization overhead Proposed Random multicast A hybrid approach Random multicast + Random poll

10. 10 Experiment Server 6 of 147Mhz 2 of dual 167Mhz Multi-node performance Comparison of load collection policies Effectiveness of RSRC func.

11. 11 Conclusion Study adaptive load balancing strategy Consider both I/O & CPU load factor On non-uniform cluster Hybrid node selection & collection policy

12. 12 Critique SWEB does not consider non-uniform cluster? RSRC correctness Parameter, threshold value decision Multicast overhead How about Broadcast & selective catch