It kinda depends what availability means? That .001% unavailability might be degraded service, might be .001% of clients having a bad time across the entire year, might be 'acts of god' (i.e. broken CPUs and the like). This kind of service is also usually fairly low down on the stack, and higher level applications can usually degrade gracefully. If they couldn't, complex applications such as Google would fail to operate; there's always _something_ broken.