Monday, February 18, 2008

Hosting Uptime/Downtime Calculation

While searching for hosting companies for a number of websites I'm working on, I noticed that a lot companies in Spain try to sell 99.5% guaranteed uptime as being very little downtime. Since this seemed like less than the average to me, I figured I might do a little calculation.

guaranteed uptime max downtime downtime / week downtime / month downtime / year
99% 1% 1.68 hours 7.2 hours 3.65 days
99.5% 0.5% 50.4 minutes 3.6 hours 1.825 days
99.9% 0.1% 10.08 minutes 43.2 minutes 8.76 hours
99.99% 0.01% 1.008 minutes 4.32 minutes 52.56 minutes
99.999% 0.001% 6.048 seconds 25.92 seconds 5.256 minutes
99.9999% 0.0001% 0.6048 seconds 2.592 seconds 31.536 seconds
99.99999% 0.00001% 0.06048 seconds 0.2592 seconds 3.1536 seconds

While most of these scenarios are not really realistic, it is interesting to see what companies are really offering. Reading about the recent Amazon S3 outage makes one want to place things into context. Amazon's goal is to offer 99.9% uptime, which means a maximum of 0.1% downtime and therefore not more than 43.2 minutes of downtime per month. The outage took little more than 2 hours which qualifies it as a 99.5% host this month. That's a long way from the 99.999% they should be offering for cloud computing indeed.


Sonia Rizvi said...
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Aeldra Robinson said...
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