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Comment by freerobby | Hacker News Reader

It is absolutely affecting more than one availability zone. Just because people didn't lose boxes outside of one AZ doesn't mean there weren't service disruptions outside of it. I know multiple people, myself included, who STILL cannot launch new instances anywhere in US-East. The EC2 web console and API have also been down intermittently and throwing errors for hours.

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If one availability zone is down, there will be suddenly be ton of extra people trying to start new instances in the other availability zones. Could there just be a shortage of available instances in the other availability zones? Perhaps Amazon don't keep enough spare capacity for this eventuality (nor would I expect them to)?

This certainly can happen. You can't rely on being able to launch enough replacement instances if a zone fails.

You can at least mitigate it by keeping utilization of your instances below what would be needed to handle load of one zone failing. I suspect to save money, many people are pushing utilization as high as possible.

This is what reserved instances are for. You can by low use reserved instances for disaster planning.

If an outage in one zone causes a brownout in the other zones, then the aren't independent "availability" zones in any logical sense. They may as well be on the same power supply.

They are independent IF you buy them in advance. If you wait till an actual outage then it's too late.

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