Why does Amazon charge like this? It seems like on the rare occasion that you ne...

tveita · on March 11, 2015

I think it makes most sense to think of it as paying for access to the tape robot.

If Amazon store your data in a tape archive (I don't know if they do, but they at least seem to have similar constraints), they can only access a small portion of the stored data at a time, so they need to control how often people request data.

They could just rate limit everyone, but this way allows people to pay for priority in an emergency while still discouraging everyday read requests.

The pricing makes more sense if you're a large user with data spanning several tapes than if you're in the single terabyte range, but the low limit still discourages you from making requests causally, which helps them keep their SLA.

If they predict that you'll trickle out your small file, they can just read out everything on the first access and cache it online, so there's no extra trips to the archive for them.

breakingcups · on March 12, 2015

Note: The following is speculation best I know. I'm recalling from memory what I've read on the internet written by someone who did not have a direct source.

Glacier uses low-speed (5400 RPM) consumer drives, which they then clock down lower to save energy. Any given 'rack' only has enough power to power a few drives on that rack, the rest is powered down.

To prevent multiple customers from all trying to pull their data out they needed to introduce a rate limiting system, which they did with this exorbitant pricing.

discodave · on March 11, 2015

You assume Glacier uses tape storage... But the same principle still applies, they're trying to prevent people clogging up the network so when somebody does need to do an emergency restore there is lots of spare network capacity.