Nines are not enough: meaningful metrics for clouds
Nines are not enough: meaningful metrics for clouds Mogul & Wilkes, HotOS’19
It’s hard to define good SLOs, especially when outcomes aren’t fully under the control of any single party. The authors of today’s paper should know a thing or two about that: Jeffrey Mogul and John Wilkes at Google1! John Wilkes was also one of the co-authors of chapter 4 “Service Level Objectives” in the SRE book, which is good background reading for the discussion in this paper.
The opening paragraph of the abstract does a great job of framing the problem:
Cloud customers want strong, understandable promises (Service Level Objectives, or SLOs) that their applications will run reliably and with adequate performance, but cloud providers don’t want to offer them, because they are technically hard to meet in the face of arbitrary customer behavior and the hidden interactions brought about by statistical multiplexing of shared resources.
When it comes to SLOs, the interests of the customer and the cloud provider are at odds, and so we end up with SLAs (Service Level Agreements) that tie SLOs to contractual agreements.
What are we talking about
Let’s start out by getting some terms straight: SLIs, SLOs, SLAs, and Continue reading

