High Availability - Terminology (I)

System

A system is composed of a collection of interacting components. A component may itself be a system, or it may be just a singular component. Components are the result of system decomposition chiefly motivated to aid in the partitioning of complex systems for either technical, or very often, for organizational or business reasons. Decomposition of systems into components is a recursive exercise. All components are typically delineated by the careful specification of their inputs and outputs and a component that is not decomposed further is called an atomic component.

Service

A system provides one or more services to its consumers. A service is the output of a system that meets the specification for which the system was devised, or which agrees with what system users has perceived the correct values to be.

Failure

A failure in a system occurs when the consumer (human or non-human) of a service is affected by the fact that the system has not delivered the expected service. Failures are incorrect results with respect to a specification or unexpected behavior perceived by the consumer or user of a service. The cause of a failure is said to be a fault.

Mean time to failure (MTTF)

Hardware reliability can be predicted by statistically analyzing historical data. The longer a component operates, the more it is likely to fail due to aging. The mean time to failure of a component is just that: a statistical forecast to measure the average time between failures with the modeling assumption that the failed system is not repaired. The greater the MTTF of a component, the less likely it is to fail. You can use the MTTF of a component (if it is known) as useful information for establishing preventative maintenance procedures and its value for an overall system can be improved by carefully selecting your hardware and software.

MTTF is the number of total hours of service of all devices divided by the number of devices.

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High Availability - Overview

Definition of High Availability

High Availability (HA) is the ability of a system to perform its function continuously (without interruption) for a significantly longer period of time than the reliabilities of its individual components would suggest. HA, then, is a trade-off between the cost of downtime and the cost of the protective measures that are available to avoid or reduce downtime.

The term High Availability, when applied to computer systems, means that the application or service in question is available all the time, regardless of time of day, location and other factors that can influence the availability of such an application.

In general, HA it is the ability to continue a service for extremely long durations without any interruptions. Hence, HA is a system design approach and associated service implementation that ensures a prearranged level of operational performance will be met during a contractual measurement period.

HA systems should protect companies from two possible failures: system failures and site failures. Though true HA solutions should guard against both system and site failures, usually HA systems are regarded as protection from system failure, while site failure is typically protected by a Disaster Recovery (DR) system.

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The Future of Computers - Artificial Intelligence

What is Artificial Intelligence?

The term “Artificial Intelligence” was coined in 1956 by John McCarthy at the Massachusetts Institute of Technology defining it as the science and engineering of making intelligent machines.

Nowadays it’s a branch of computer science that aims to make computers behave like humans and this field of research is defined as the study and design of intelligent agents where an intelligent agent is a system that perceives its environment and takes actions that maximize its chances of success.

This new science was founded on the claim that a central property of humans, intelligence—the sapience of Homo Sapiens—can be so precisely described that it can be simulated by a machine. This raises philosophical issues about the nature of the mind and the ethics of creating artificial beings, issues which have been addressed by myth, fiction and philosophy since antiquity.

Artificial Intelligence includes programming computers to make decisions in real life situations (e.g. some of these “expert systems” help physicians in the diagnosis of diseases based on symptoms), programming computers to understand human languages (natural language), programming computers to play games such as chess and checkers (games playing), programming computers to hear, see and react to other sensory stimuli(robotics) and designing systems that mimic human intelligence by attempting to reproduce the types of physical connections between neurons in the human brain (neural networks).

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