IEC: On-Line Education: WPF: Building Carrier Grade Applications Using a Highly Available Database Management System

Web ProForums

Home / On-Line Education / Web ProForums

Building Carrier Grade Applications Using a Highly Available Database Management System

Sponsored by:

Table of Contents:

Introduction

1. Defining Availability

2. Redundancy: The Key to Carrier-Grade Availability

3. Preserving Application State: Two Techniques

4. Highly Available Database Managers

5. A Sidebar on How an RDBMS Works

6. Understanding Safeness Levels

7. Data Loss Considerations

8. MTTR Considerations

9. Application Throughput Considerations

10. Three-Way Tradeoff Summary

10. Three-Way Tradeoff Summary

A summary of these three trade-offs is shown in Figure 15.

	Data Loss	MTTR	App Throughput
1-Safe	Likely	High Unpredictable	High
2-Safe Received	Only if 2 failures	Moderate, Unpredictable	Medium
2-Safe Durable	No	Low Deterministic	Low for writes High for reads

Figure 15: Three-Way Tradeoff Summarized

Summary

System availability is determined by both MTBF and MTTR. In some applications, availability requirements exceed the availability of standard hardware (and software) components. Such systems must use redundant hardware. In order to support rapid recovery, application state must persist even though primary hardware (or software) fails. Highly available database managers provide a superior way to guarantee state persistence. They offer a 3-way tradeoff between data safety, MTTR and application throughput. Designers must chose a point on this 3-way continuum for their highly available applications.

Self-Test >>