Achieving “Six Nines” When You Launch

By | 2017-12-09T00:04:34+00:00 September 1st, 2009|Design of Experiments, Rules of Thumb, skmurphy|0 Comments

High availability is often expressed as “nines”, or the percentage of availability in a year. Six nines is 99.9999% uptime or no more than 31.5 seconds of downtime in a year.

Achieving “Six Nines” When You Launch

High availability is an increasing requirement for SaaS vendors. Availability is often expressed at “nines”, or the percentage of availability in a year. The following handy table gives you a quick decode to the most common nines.

“Number of Nines” Availability as a Percentage Max Time in a Year
Three Nines 99.9% 8.76 hours
Four Nines 99.99% 52.6 minutes
Five Nines 99.999% 5.26 minutes
Six Nines 99.9999% 31.5 seconds

Note that “six sigma” is normally defined to allow a process variation of plus or minus 1.5 sigma so that it’s actually 4.5 sigma in a “normal distribution” which is 99.99966 which is pretty close to “six nines.” A true “six sigma” is “nine nines” or 99.9999999%

How to Achieve Six Nines in 2009

I was talking to a SaaS startup planning to launch this month and I suggested that they could achieve six nines if they launched at the right time this month:

9:09:09 9/9/9

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