High availability. What does it exactly mean ?

Maybe like me you are used to read architecture documents that state that an application should have high availability. It’s not uncommon to read that an application should have four-nine availability (99,99%). But what does it really mean ? In the JBoss in Action book there is a very clear explanation by giving the allowed downtime per year. Here is the table : Uptime Allowed downtime per year 99% 87.6 hours 99.9% 8.8 hours 99.99% 53 minutes 99.999% 5.3 minutes 99.9999% 31 seconds 99.99999% 3.1 seconds 3.1 seconds downtime per year, it’s really not a lot. So if you sign a contract with 99.99999% availability, make sure you have good lawyers around you.

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Coding the architecture

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I’ve been invited to London by Skills Matter to follow their 2 days workshop called : Coding the architecture. This workshop has been created by Simon Brown and Kevin Seal. The workshop was given by Simon. Actually, that’s one thing I really like with Skills Matter : they spot the people who are knowledgeable about one topic and help them […]

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Looking for a definition of an architect

On top of my J2EE consultancy work, I teach one evening a week at university. The topics I cover go from UML modelling, Design Patterns, Refactoring, Java APIs, Servlets, JSP, XML, EJBs, XML to Web Services . My students have to do a weekly exercise and therefore have to model and write lots of Java classes (and refactor them from time to time). At the end of the year, I always have the same question: « Will I have to do all this work if I become an architect? » In my students heads, an architect is someone who doesn’t write code anymore (even better, someone who never had to write a line in his/her entire life, not even a Hello World). I try to tell them that it’s difficult to link customers, project leaders and developers without having any technical background. One day I was so frustrated, that in my following class I introduced two new slides so we could talk about it. Here is the content (picked up from Enterprise Architect for J2EE Technology book): “The ideal architect should be a person of letters, a mathematician, familiar with historical studies, a diligent student of philisophy, acquainted with music, not ignorant of medecine, learned in the responses of juriconsults, familiar with astronomy and astronomical calculations – Vitruvius, 25 BC” After lots of laughter I showed them the following slide which contains more accurate information based on our job (Software […]

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