[space-monkey]

The tradeoff is in that AZs are "engineered to be insulated" as opposed to being actually, or naturally isolated. Prior to their downtime, I've had plenty of conversations with folks that I work with about AWS and we've always assumed that AZs are not 100% isolated. I can see how someone can read "engineered to be insulated" the other way, but I generally read these kinds of materials as guaranteeing nothing beyond the most limited possible reading, and probably not even that.

The quoted statement doesn't say that isolation is 100% or that multiple AZs can't ever ever fail at the same time. It says that if only one AZ goes down and you have servers in another, then those servers will still be up, which should be obvious. Insulated doesn't even mean the same thing as isolated.

[ra]

Sure, I don't disagree with what you are saying. However I think that the way Amazon presents the concept of an AZ is that it IS isolated from other AZ's in the same region.

Even the name, 'Availability Zone' implies that it is isolated from other 'Availability Zones' in the same region. And that text I quoted does nothing but substantiate that inference.

I just think that Amazon are misleading here. Maybe they shouldn't call it an Availability Zone.