Service Availability: Principles and Practice

Chapter 9

Model-Based Software Management: The Software Management Framework

Maria Toeroe

Ericsson, Town of Mount Royal, Quebec, Canada

9.1 Introduction

The key expectations toward a system providing Service Availability (SA) is that its services are available to their users virtually any time, be it at 3 a.m. on a Sunday night or 3 p.m. on Thursday afternoon. While a couple of decades ago only few services had to satisfy this requirement, today with the Internet becoming the infrastructure for all aspects of life the possibility of shutting down the system for maintenance and software upgrades has long gone. Moreover with the Internet's global reach even the notion of slow business hours is fading away quickly: 3 a.m. in North-America means 3 p.m. at the other side of the globe with all its urgency that is not localized any more.

Nevertheless the maintenance and upgrades still have to be carried out somehow at some point and the Software Management Framework (SMF) [49] of the SA Forum offers an approach to resolve this conflict.

As we have discussed in Chapter 6 the Availability Management Framework (AMF) [48] is already designed so that it is capable of maintaining SA in the presence of a failure. The solution is based on the redundancy introduced to the system so that services provided by a failing component can be failed over to another healthy component standing by for exactly this purpose. Luckily just because we introduced this redundancy our component should not fail more ...