Yes, this. Infiniband has scaled up significantly since then as well. I believe you can do 4x25 (100Gb) today.

Having this background knowledge gives you a much better idea of why the interconnects is going to be such a big problem going forward.... When I was working with QDR IB 5 years ago, it didn't matter if they had faster cards - the PCI bus at the time couldn't support anything faster. So you were literally riding the edge of the I/O capability all the way through the stack.

This is different to the sort of thing Google is doing in the data centre. Most of the PBs/sec don't really see the light of day since you may have a multi-megabyte "image" being captured at something like 40MHz, but practically much of the image is zeros for any given capture. So zero-suppression in the first instance already brings the data down to much more manageable numbers, before they hit off-the-shelf computing hardware.

(At least, that was the case a few years ago. I don't know how much it has changed but I would be surprised if they had totally overhauled things).