How hard is 99.999% availability? The GoDaddy outages.

On June 22, 2010 GoDaddy suffered a four hour outage.  On June 14, 2011 they were down for three hours, and recently on Sept 10, 2012 their DNS service was down for 6 hours.

What is their availability rating for these three years, assuming no other outages?  The calculation is easy. Three years equals 26,298 hours.  They were down 13 hours, and up 26,285 hours.  Their availability is 26285/26298 = 99.95%.  or about three nines.

Now GoDaddy promises its DNS customers 99.999% availability.  If we just focus on their DNS service, with its recent 6 hour outage, how many years, counting 2012, will it take for 100% DNS up-time, to recover to this five nines goal?  Well, there are 8766 hours per year, so we need to solve (8766*n – 6)/(8766*n) = 0.99999.  The answer is a staggering n = 68.45 years!

Well, there is mathematics and there is marketing. After 10 years of perfect up-time, I’m sure any company would advertise “Ten years of perfect up-time” and sweep the previous outages under the rug.  This might even be reasonable from a practical point of view, at least after ten years.  That said, with the cloud vendors and even the infrastructure vendors struggling to get over three nines, how does a company that needs five nines make its decisions?

The answer of course is to never put all you eggs in one basket.  In the era of immature cloud computing, it will be a challenge, and this challenge will be expensive.


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