Beyond Redundancy

Eric Bauer is Reliability Engineering Manager in the IMS Solutions Organization of Alcatel-Lucent, where he focuses on reliability of Alcatel-Lucent's IMS solution and the network elements that comprise the IMS solution. He has written Design for Reliability: Information and Computer-Based Systems and Practical System Reliability. Randee Adams is a Consulting Member of Technical Staff in the Applications Group of Alcatel-Lucent. Currently, she is focusing on reliability for Alcatel-Lucent's software applications.Daniel Eustace is a Distinguished Member of Technical Staff in the IMS Solutions Organization of Alcatel-Lucent. Currently, he is a solution architect focusing on reliability, key quality indicators, geographical redundancy, and call processing.

• Figures xv Tables xixEquations xxiPreface and Acknowledgments xxiiiAudience xxivOrganization xxivAcknowledgments xxviPART 1 BASICS 11 SERVICE, RISK, AND BUSINESS CONTINUITY 31.1 Service Criticality and Availability Expectations 31.2 The Eight-Ingredient Model 41.3 Catastrophic Failures and Geographic Redundancy 71.4 Geographically Separated Recovery Site 111.5 Managing Risk 121.6 Business Continuity Planning 141.7 Disaster Recovery Planning 151.8 Human Factors 171.9 Recovery Objectives 171.10 Disaster Recovery Strategies 182 SERVICE AVAILABILITY AND SERVICE RELIABILITY 202.1 Availability and Reliability 202.2 Measuring Service Availability 252.3 Measuring Service Reliability 33PART 2 MODELING AND ANALYSIS OF REDUNDANCY 353 UNDERSTANDING REDUNDANCY 373.1 Types of Redundancy 373.2 Modeling Availability of Internal Redundancy 443.3 Evaluating High-Availability Mechanisms 524 OVERVIEW OF EXTERNAL REDUNDANCY 594.1 Generic External Redundancy Model 594.2 Technical Distinctions between Georedundancy and Co-Located Redundancy 744.3 Manual Graceful Switchover and Switchback 755 EXTERNAL REDUNDANCY STRATEGY OPTIONS 775.1 Redundancy Strategies 775.2 Data Recovery Strategies 795.3 External Recovery Strategies 805.4 Manually Controlled Recovery 815.5 System-Driven Recovery 835.6 Client-Initiated Recovery 856 MODELING SERVICE AVAILABILITY WITH EXTERNAL SYSTEM REDUNDANCY 986.1 The Simplistic Answer 986.2 Framing Service Availability of Standalone Systems 996.3 Generic Markov Availability Model of Georedundant Recovery 1036.4 Solving the Generic Georedundancy Model 1156.5 Practical Modeling of Georedundancy 1216.6 Estimating Availability Benefit for Planned Activities 1306.7 Estimating Availability Benefit for Disasters 1317 UNDERSTANDING RECOVERY TIMING PARAMETERS 1337.1 Detecting Implicit Failures 1347.2 Understanding and Optimizing RTO 1418 CASE STUDY OF CLIENT-INITIATED RECOVERY 1478.1 Overview of DNS 1478.2 Mapping DNS onto Practical Client-Initiated Recovery Model 1488.3 Estimating Input Parameters 1548.4 Predicted Results 1658.5 Discussion of Predicted Results 1729 SOLUTION AND CLUSTER RECOVERY 1749.1 Understanding Solutions 1749.2 Estimating Solution Availability 1779.3 Cluster versus Element Recovery 1799.4 Element Failure and Cluster Recovery Case Study 1829.5 Comparing Element and Cluster Recovery 1869.6 Modeling Cluster Recovery 187PART 3 RECOMMENDATIONS 20110 GEOREDUNDANCY STRATEGY 20310.1 Why Support Multiple Sites? 20310.2 Recovery Realms 20410.3 Recovery Strategies 20610.4 Limp-Along Architectures 20710.5 Site Redundancy Options 20810.6 Virtualization, Cloud Computing, and Standby Sites 21610.7 Recommended Design Methodology 21711 MAXIMIZING SERVICE AVAILABILITY VIA GEOREDUNDANCY 21911.1 Theoretically Optimal External Redundancy 21911.2 Practically Optimal Recovery Strategies 22011.3 Other Considerations 22812 GEOREDUNDANCY REQUIREMENTS 23012.1 Internal Redundancy Requirements 23012.2 External Redundancy Requirements 23312.3 Manually Controlled Redundancy Requirements 23512.4 Automatic External Recovery Requirements 23712.5 Operational Requirements 24213 GEOREDUNDANCY TESTING 24313.1 Georedundancy Testing Strategy 24313.2 Test Cases for External Redundancy 24613.3 Verifying Georedundancy Requirements 24713.4 Summary 25414 SOLUTION GEOREDUNDANCY CASE STUDY 25614.1 The Hypothetical Solution 25614.2 Standalone Solution Analysis 25914.3 Georedundant Solution Analysis 26314.4 Availability of the Georedundant Solution 26914.5 Requirements of Hypothetical Solution 26914.6 Testing of Hypothetical Solution 277Summary 285Appendix: Markov Modeling of Service Availability 292Acronyms 296References 298About the Authors 300Index 302