Basic Tenets of Availability
I wanted to start a discussion around availability and how networks have to be engineered as we look forward. To do this I thought I would devote this blog to discussing some basic tenants of availability. Availability is the opposite of downtime, where downtime is a measure of the percentage of time something is un-available something is, availability is the percentage of time it is actually useable. It is often expressed in “nines”, such as; it is available for five nines (99.999). This means it is available 99.999% of the time. It is often better to think about what the un-availability is. Five nines (99.999) is about 5 minutes per year, three nines is a little over 8 hours per ...
