Availability - What it really means?
Metrics are critical for all cloud services. One of the most common metric that is tracked by most cloud services is the availability metric. The general definition of the availability is the “the quality of being able to be used or obtained”. The key part of availability is “quality” but definition of quality is vague. So, I always wondered how different services choose to implement this? If a cloud service is serving multiple types of requests, should the availability values for each request type be considered in evaluating availability? Some type of requests are called more often than others, are all these request types equally important? Each request made by the customer has a time delay between customer sending the request and getting a response for it, does time delay play into the availability metric or is it just number of requests that got a response? What is the time scale that should be considered for the metic? Is it seconds, minute, hour, day, week, or month or something e...