Posted By: Darren Bonawitz, principal of 1102 GRAND
We get this question a lot from prospective customers so I thought I would post this datacenterjournal.com. article, “What Do All Those Nines Mean? In short, don’t base your collocation decision purely on one criteria. The decision on where to collocate or how to design your data center is so much more complicated than that. The same thing goes with the Tier I – IV structure as these inflexible terms are just good for broad comparisons and don’t ever tell the whole story. One facility that can claim 99.99% uptime is not the same as another although many people think that is what it means. Likewise, there are Tier II data centers that are a better fit than some Tier IIIs for some companies. At the end of the day, your business should opt for a collocation environment that is right-sized for not only your uptime and reliability (not all businesses are the same) and your budget.
According to the article, “High availability is critical to many modern IT infrastructures, but the most common means of measuring it—percent availability, or by the “nines”—can be misleading. Availability is often listed as some collection of nines: 99.9% (three nines), 99.9% (four nines) and 99.999% (five nines). Each corresponds to the percentage of time that an IT infrastructure is available: three nines corresponds to about 8.76 hours of downtime a year, four nines corresponds to only about 53 minutes of downtime a year and five nines corresponds to about 5 minutes of downtime a year.”