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Comment by reustle | Hacker News Reader

They keep saying it happened in a single availability zone when I saw frantic tweets from people in 1A, 1C and 1D.

AWS hides the real availability zone names from you. From the docs:

Can I assume that my Availability Zone us-east-1a is the same location as someone else's Availability Zone us-east-1a?

No. Currently, we do not support cross-account proximity. Each account's Availability Zones are independent. For example, the us-east-1a Availability Zone for one account might be in a different location than for another account.

http://docs.amazonwebservices.com/AWSEC2/latest/UserGuide/FA...

Everyone's A zone is different. So I could say A is down while someone else is saying B, and we could be talking about the exact same zone. It makes it difficult to say if it is more widespread or not.

You can match them up through a quirk in one of the APIs.

http://alestic.com/2009/07/ec2-availability-zones

My us-east-1a is the affected zone, which is 3a98bf7d-126d-411a-a612-3a57a62dc688 using the incantation on the site.

(Oh, and to note: my us-east-1a was also the affected zone during the massive outage last year, and I believe I remember another outage sometime between then and now. I almost feel like every Amazon outage affects my zone. I kind of wonder if that availability zone just sucks ;P.)

Maybe I'm assuming wrong but I guess in your example zone A and B are the same and that the different zone names users see don't represent different ways of spreading resources. If so, why aren't they named consistently? If not, are there any details on how and why they've set up their zones (or am I overlooking another assumption I've made?)

If they weren't different it would likely everyone would just pick the same first zone, this way they can randomly assign resources keeping it even.

Due to a quirk of both human nature and copy/paste example code, if the names of the availability zones were mapped the same for all users then 90% of requests would be to the zone named "A". To make certain that the zones get even usage, as they bring on new customers, they change the A-D order of the availability zones as seen by these new accounts.

Adding to the "why it's scrambled" comments: because data transfer pricing differs for intra- vs. inter- AZ traffic, if you need to coordinate with other entities to be in the same AZ, it's possible to do so.

But, yes, generally: Amazon randomly allocates AZ labels to given customers to avoid preferential clustering on any given first choice.

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