A couple of people asked me what is the difference between 99% and 99.999% they see on different SLAs ?
The answer is … 0.999%!
That is the funny answer. The actual answer is:
– 99% Availabilty = 3.65 days downtime
– 99.9% Availabilty = 8.76 hours downtime
– 99.99% Availabilty = 52.6 minutes downtime
– 99.999% (AKA the 5 nines) Availabilty =5.26 minutes downtime
So there difference between 99% uptime and 99.999% is over 3 and half days of downtime. Some business are okay with it, others this is not an option. So it always good to explain to cusomers the difference in initial meetings as the design will be influnced by how many nines they want.
Sounds basic, but amazingly enough misunderstood often.
Some food for thought.
Thanks for reading.