1. CS848 Class Project: A Survey on QoS for Multi-tier Web Systems Huaning(Mike) Nie 2006.11.29

2. Agenda  Motivation  Background QoS in General Multi-tier Architecture  QoS for Multi-tier Web System  Proposed Solutions  Future Work

3. Motivation  More and more information service system emerge on the Internet.  Many of these service systems exhibit poor quality, such as: Unpredictable response time Useless query result  Unsuitable for mission-critical applications

4. Background: QoS in General  A traffic engineering term  A list of control mechanisms that can provide different level of priority to different customers;  Or Guarantee a certain level of performance to a data flow.  Applications require QoS: streaming multimedia, voice over IP, etc.

5. Background: Multi-tier Architecture  An extension of the classic client- server model  Usually three tiers: presentation, business services, data services  More complex logic, high scalability, easy deployment

6. QoS for Multi-tier System  Paper: Weikum, G. Towards guaranteed quality and dependability of information services, 1999  System-centric: Reliability Availability  MTTF/(MTTF+MTTR) Response time goal Throughput

7. QoS for Multi-tier System  Information-centric Accuracy Comprehensiveness Timelineness  Note: For some application the customer may only be interested in a portion of the query result.

8. This VS QoS for Streaming Multimedia  Key differences: QoS parameters Deliverables: query result VS video or audio Main bottleneck

9. Proposed Solutions  System-centric Reliability + Availability  Using replicas Response time goal:  Scheduling  Queuing  Resource allocation adjustment Buffer memory allocation, disk access control, etc.

10. Proposed Solutions  Information-centric Timelineness (Currency)  “ Good enough in SQL ” paper

11. Proposed Solutions  Combined system and information goals: Paper: Braumandl, R. Quality of service in an information economy, 2003 Consider QoS in Query optimization, plan instantiation and plan execution.

12. Future Work  More approaches for information- centric requirement  More approaches for database fast recovery  Suggestions