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Should the datacenter be in the middle? (posted 2023-09-07)

The other day, I landed on this article: In Focus: Subsea Network Architecture: IXPs. The article takes some time to arrive at the point that undersea internet exchanges would be a good idea. The most eyecatching part is a variation on this image:

As the article starts out discussing how datacenters have been moving away from large cities to take advantage of opportunities such as space, cheap energy and easier cooling, this image seems to suggest that these blue dots in are good locations for datacenters and/or internet exchanges in general. And that's definitely not the point of the paper that the image is from.

That paper is very specifically about the best locations to place servers for high speed algorithmic trading on multiple markets some distance away from each other. This immediately explains why there is nothing around the western US: there are simply no stock exchanges / markets there (the red dots in the image).

The math looks more complicated, but presumably, in these cases it helps when the servers executing the trading algorithms are in the middle between the "users", rather than close to one and further from the other(s).

If you need data from two places far away from each other, then it's better when each is 25 milliseconds away, as you can then complete your action in 25 ms plus however long it takes to do your own processing. If you're close to one so it's 0 ms for one data source and 50 ms for the other, then the entire action takes at least 50 ms.

But is that a common situation?

In general, you can just copy the data beforehand. So this only applies if you're using "live" data from two or more locations. Videoconferencing with a number of participants could be an example, where a server receives the video from all the participants, mixes it into a single feed and then sends that single feed out to all the participants. If the server is in the middle, this limits the maximum delay. I guess that could be somewhat helpful. But to the degree that it makes sense to have datacenters in the middle of the ocean? I'm not convinced.