Close. Tiered, yes. But remember who we're talking about.
First, no tape. The areal storage density of tape is lower than hard disks. Too many moving parts involved. Too hard to perform integrity checks on in a scalable, automated fashion without impacting incoming work.
Second, in order to claim the durability that they do (99.999999999%), that means every spot along the pipe needs to meet those requirements. That means the "near-line HDD array" for warm, incoming data needs to meet those requirements. Additionally, if the customer has specified that the data be encrypted, it needs to be encrypted during this staging period as well. It also needs to be able to scale to tens if not hundreds of thousands of concurrent requests per second (though, for something like Glacier, this might be overkill).
They've already built something that does all that. It's called S3. The upload operations likely proxy to S3 internally (with a bit of magic), and use that as staging space.
First, no tape. The areal storage density of tape is lower than hard disks. Too many moving parts involved. Too hard to perform integrity checks on in a scalable, automated fashion without impacting incoming work.
Second, in order to claim the durability that they do (99.999999999%), that means every spot along the pipe needs to meet those requirements. That means the "near-line HDD array" for warm, incoming data needs to meet those requirements. Additionally, if the customer has specified that the data be encrypted, it needs to be encrypted during this staging period as well. It also needs to be able to scale to tens if not hundreds of thousands of concurrent requests per second (though, for something like Glacier, this might be overkill).
They've already built something that does all that. It's called S3. The upload operations likely proxy to S3 internally (with a bit of magic), and use that as staging space.
After that, the bottleneck is likely I/O to Glacier's underlying storage - but again, not tapes. See this post for deets: http://news.ycombinator.com/item?id=4416065