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Comment by s_dev | Hacker News Reader

So why do they pride themselves on a 99.9% uptime if downtime is common and normal?

Uptime has nothing to do with anything in the real world. It's a number you put in an SLA of how much downtime is acceptable before they start paying you back money. And 99.9% still means 43 minutes of downtime every month. And even after that it's a calculation of risk. What does full redundancy cost vs paying back the fees for a say 24 hours of downtime? A lot of the time paying back money is way way cheaper then actually investing in technical redundancy.

99.9% uptime is still more than 40 minutes downtime per month. According to their status page they are at 99.93% uptime for the current quarter even with the current incident.

They wait multiple hours after failure before updating their status page, so their actual uptime is lower.

The 99.9% claims is likely on the actual uptime, not on the time the status page claimed to be up.

99.9% = 8.77 hours per year

Multiply that out by 1000s of providers.

Downtime is not the same as service disruption

huh?

A service might be unavailable due to an intentional downtime for maintenance. This is often hidden by various redundancies but certain bottlenecks may remain.

You've just intentionally disrupted the service then.

You can announce downtime for a certain capacity of a service ahead of time. Which is essentially planned maintenance with some capacity hit, but when it's unplanned it's called disruption. Also, generally disruptions come with a bigger capacity loss, even if you don't lose the service outright.

These terms are not limited to cloud infrastructures and not new either. Computation clusters use these terms for at least 12-13 years (from my experience) or for even longer.

Ah, you must work for Amazon ;)

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