Can you expect a service to be down? Is this considered a 24/7 service? Some people like to look at periods of acceptable downtime when measuring availability, but how useful is this to someone calling your service? I should either be able to rely on your service responding or not. Measuring periods of downtime is really more useful from a historical reporting angle. Durability of data How much data loss is acceptable? How long should data be kept for? This is highly likely to change on a case-by-case basis.
