High-availability using open source software

Availability, the degree to which a system is in a specified, operable state, is a critical criterion in overall information systems' quality. Since network services are the core infrastructure components for any modern business, their uninterrupted functioning becomes the critical issue in sustaining the business itself. Deployment of a production ready system to ensure high availability is not an easy task. Additionally, implementation of highly available software solution using existing resources, without or with minimal investment is a common requirement in many business environments. Various commercially available solutions exist on the market, but the open source community also provides a number of mature, production-ready tools and techniques aiming at the same market. Comparing the TCO of both solutions, the open source approach represents the most economical, but nevertheless reliable solution. This paper gives an overview of the most commonly used tools and techniques to ensure high availability of information systems' network services using only open source software.