Meaningful availability, Hauer et al., NSDI’20
With thanks to Damien Mathieu for the recommendation.
This very clearly written paper describes the Google G Suite team’s search for a meaningful availability metric: one that accurately reflected what their end users experienced, and that could be used by engineers to pinpoint issues and guide improvements.
> A good availability metric should be meaningful, proportional, and actionable. By "meaningful" we mean that it should capture what users experience. By "proportional" we mean that a change in the metric should be proportional to the change in user-perceived availability. By "actionable" we mean that the metric should give system owners insight into why availability for a period was low. This paper shows that none of the commonly used metrics satisfy these requirements…
The alternative that Google settled on is called windowed user-uptime and it’s been used in production across all of G Suite for the past year. We’ll look at how windowed user-uptime works in a moment, but first let’s review commonly used approaches to availability reporting and why they failed Google’s test.
Counting nines
The basic form of an availability metric is the ratio of ‘good’ service to the total demanded service: Continue reading