Comment by Twirrim
I can't talk about it, but I've yet to see an accurate guess at how Glacier was originally designed. I think I'm in safe territory to say Glacier operated out of the same data centers as every other AWS service.
It's been a long time, and features launched since I left make clear some changes have happened, but I'll still tread a little carefully (though no one probably cares there anymore):
One of the most crucial things to do in all walks of engineering and product management is to learn how to manage the customer expectations. If you say customers can only upload 10 images, and then allow them to upload 12, they will come to expect that you will always let them upload 12. Sometimes it's really valuable to manage expectations so that you give yourself space for future changes that you may want to make. It's a lot easier to go from supporting 10 images to 20, than the reverse.
Im like 90% sure ive seen folks (unofficially) disclose the original storage and API decisions over the years, in roughly accurate terms. Personally I think the multi dimensional striping/erasure code ideas are way more interesting than the “its just a tape library” speculation/arguments. That and the real lessons learned around product differentiation as supporting technologies converge.