CS848 Class Project:

A Survey on QoS for Multi-tier Web Systems

Huaning(Mike) Nie2006.11.29

Agenda

Motivation Background

QoS in General Multi-tier Architecture

QoS for Multi-tier Web System Proposed Solutions Future Work

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

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.

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

QoS for Multi-tier System Paper: Weikum, G. Towards guaranteed qual

ity and dependability of information services, 1999

System-centric: Reliability Availability

MTTF/(MTTF+MTTR) Response time goal Throughput

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.

This VS QoS for Streaming Multimedia

Key differences: QoS parameters Deliverables: query result VS video or

audio Main bottleneck

Proposed Solutions

System-centric Reliability + Availability

Using replicas Response time goal:

Scheduling Queuing Resource allocation adjustment

Buffer memory allocation, disk access control, etc.

Proposed Solutions

Information-centric Timelineness (Currency)

“Good enough in SQL” paper

Proposed Solutions

Combined system and information goals: Paper: Braumandl, R. Quality of service in an

information economy, 2003 Consider QoS in Query optimization, plan ins

tantiation and plan execution.

Future Work

More approaches for information-centric requirement

More approaches for database fast recovery

Suggestions