My knowledge is a decade old, so they very well may be using tape now, but were not originally. At announcement time Glacier was using super dense racks of har

My knowledge is a decade old, so they very well may be using tape now, but were not originally. At announcement time Glacier was using super dense racks of hard disks but only powering a subset of them. This led to some tape-like behaviors, like your restore request might take a long time to process because your data was likely stored on disks that weren't powered on and you'd need to wait for them to come online.