Skip to main content

Posts

Showing posts from June, 2008

99.9999% How many nines are enough in mobile?

All of us have probably heard of the saying "Five Nines" which means 99.999% system availability and is the mythical reliability target often quoted as a goal to achieve when running a computer system or service. There is a larger debate on what the number means, if it is only the "network" or if it should include applications, servers, etc. I'm not going down that debate path today other than to state the obvious that the "more nines" the better. Instead I would like to use the standard availability table to describe one of the hidden realities that currently exists with mobile services. So first let's start with the table: 99.999% is 5 minutes of downtime per year, and 90% is 36.5 days of downtime per year. So now the question is: Would it be acceptable for a production mobile service to only be available 90% of the time? My company has seen examples of this low level of service from even the most well known of companies. One of the most problema