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Comment by marcosdumay | Hacker News Reader

No, that quotation on the GP clearly states that AWS has enough redundancy within the same region that they will continue all services running on it if a datacenter is destroyed.

It's very clearly not about you being able to set-up redundancy for yourself.

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That's actually true. AWS is designed to survive one datacenter being offline (which happened more than once, btw). When the first DC in ME was hit, AWS continued working normally, with only a few services experiencing issues.

But it's not designed to survive TWO datacenters going offline, and in a permanent fashion.

That's fair. The only reference was about one datacenter blowing up. You can't have unlimited redundancy.

Aren't they supposed to have 3 copies of everything? If so, two datacenters going offline at the same time should mean almost zero data loss.

Some systems in AWS do, but they typically need a quorum of at least two copies to work. Other systems only have 2 copies.

And in this case, it looks like all three DCs were damaged.

No.

_You_ are supposed to have three copies of everything - and two of those should be off AWS.

Yeah yeah I know about 3-2-1.

But when I put data on normal S3, isn't my money supposedly paying for triple redundancy?

Look, here's the documentation: https://docs.aws.amazon.com/AmazonS3/latest/userguide/DataDu...

"S3 Standard, S3 Intelligent-Tiering, S3 Standard-IA, S3 Glacier Instant Retrieval, S3 Glacier Flexible Retrieval, and S3 Glacier Deep Archive redundantly store objects on multiple devices across a minimum of three Availability Zones in an AWS Region. An Availability Zone is one or more discrete data centers with redundant power, networking, and connectivity in an AWS Region."

As far as I've heard before that's not with parity and three zones means three copies. But when I search now I see things about 5+4 parity, any insight here?

Yes, normal S3 is at least triply-redundant. But it's possible for S3 to lose some data if two DCs are down and a disk dies in the single remaining DC.

AWS doesn't use parity for S3, they actually mirror the data.

Get some training. You dont even understand the core concepts, and the difference between a data center and an availability zone...

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