Comment by jp57

The most likely explanation is that they used a tape robot, such as the one seen here:

https://www.reddit.com/r/DataHoarder/comments/12um0ga/the_ro...

Which is basically exactly what you described but the picker is a robot.

Data requests go into a queue; when your request comes up, the robot looks up the data you requested, finds the tape and the offset, fetches the tape and inserts it into the drive, fast-forwards it to the offset, reads the file to temporary storage, rewinds the tape, ejects it, and puts it back. The latency of offline storage is in fetching/replacing the casette and in forwarding/rewinding the tape, plus waiting for an available drive.

Realistically, the systems probably fetch the next request from the queue, look up the tape it's on, and then process every request from that tape so they're not swapping the same tape in and out twenty times for twenty requests.

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.

I think folks have missed what I think would have been clever about the implentation I (apparently) dreamt up. It's not that "it's just a tape library", it's that it would have used the existing FC and picker infrastructure that Amazon had already built, with some racks containing drives for removable media. I was thinking that it would not have been some special facility purely for Glacier, but rather one or more regular FCs would just have had some shelves with Glacier media (not necessarily tapes).

Then the existing pickers would get special instructions on their handhelds: Go get item number NNNN from Row/shelf/bin X/Y/Z and take it to [machine-M] and slot it in, etc.

Yeah, but they've been robotic for decades since.

They would definitely be using rubies robots given how uniform hard drives are. The only reason warehouses still have humans is that heterogeneity (different sizes, different textures, different squishiness, etc).