> They are perfect world actual hours that don't include any unexpected downtime
It isn't clear from this particular post, but considering Patrick refers to "overprovisioning" and having a "hot spare" I get the impression that they have designed their DC setup to minimize unexpected downtime. Sure, it can still happen, but with proper up-front planning what you call "perfect world" can become typical.
> or any ancillary costs outside of racking
As I see it from Patrick's post and my own colo experience, there are three groups of costs for colo that are baked in to the cost of AWS compute and storage: capital cost of hardware (Patrick has a specific line item for this); facility cost; and labor for maintaining the hardware (which is the cost under discussion. What do you think is significant, missing, and unique to colo?
