How Many Nines Do We Need?
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Service Level Agreements can be confusing, but are also critical to successful implementation and successful user support.
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Understanding the relationship between Service Level and cost helps avoid unnecessary or excess investments
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CloudStrategies helps you balance your budget and your requirements
"We guarantee five nines!!!"
Almost sounds like an impossible poker hand, but its really a service providers way of telling you that their service will be operational and available to you 99.999% of the time. Simple really.
Given that a year consists of 525,600 minutes, that means that there will be less than 5.256 minutes of downtime during a year. That's pretty fantastic, but also very expensive. The question you need to ask is whether or not your business requirements are such that your business couldn't tolerate more than five and a half minutes of unavailable systems.
Take email for example. Would your people even be aware that email was unavailable for ten minutes on any given day? Every day? Several times each day? Depending upon how your business uses email, probably not. But in a busy retail operation, if the Point of Sale system experienced even a minute of downtime it is very likely that the IT manager's life would instantly turn upside down.
Of course, you're probably thinking that having only five and a half minutes of downtime in a year sounds pretty good, so why not shoot for that anyway. If it didn't cost any more to have five nines than it did to have, say, three, that would make a lot of sense. But what if it cost ten times more? Definitely not worth it, right? That's why it is so important to carefully analyze your business requirements system by system, application by application, and determine the appropriate Service Level Agreement to establish, and invest in, for each.
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Take the email example given above. Three nines, or 99.9% uptime, equals 8.76 HOURS of possible downtime each year. But when you divide that by the number of days in a year its way less than a minute per day, so you'd likely never even notice it. Microsoft BPOS, as an example, offers a Service Level Agreement of three nines or 99.9% uptime. So the answer to the question "How Many Nines Do We Need?" depends both upon what your business requires and also upon what your business can afford. Your CloudStrategies consultant can help you analyze and determine both! |
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