In the old phone model, SLAs are per-customer: it doesn't matter what your network as a whole looks like, if any phone line goes below N 9s you're going to be p

In the old phone model, SLAs are per-customer: it doesn't matter what your network as a whole looks like, if any phone line goes below N 9s you're going to be paying out the contract penalties. It's still better for the telco to fail for fewer customers, because then they don't have to pay out as much. The granularity may be harder to define for cloud services, but it is very much doable; it's all about making sure that the target metrics have zero connection to the global state of the system.