This is a quick post to bring out two things to be sure to consider when taking that step to extending your infrastructure to a cloud service provider, and comparing the SLA between those providers.
First, calculate the offered SLA uptime on a site such as http://uptime.is/ and determine what the downtime is, and plan for what this would mean for your business and how you can have contingency plans in place. Moreover, be sure to consider what dependencies your service will have with the provider. For example, they may have a separate SLA for the storage as they do the compute, although an outage in either could potentially disrupt service. This means you practically need to consider combining the calculated down time for each dependency.
Second, and this is the one most people seem to forget. Look for those special words “service credit” as this is where the rubber meets the road in regards to them taking the uptime of your business as seriously as you do. Put simply, they are committing to back their SLA with dollars and cents!