It's not a lot, but there are a bunch of pictures on google.com/about/datacenters, including a 'street view' inside our DC in North Carolina.

There are also a bunch of papers on the network architecture, https://research.google.com/pubs/Networking.html .

But yes, a lot is closed for the obvious reason that this is really core to the business Google is running.

(I'm a datacenter engineer at Google)

There's a lot of openly available networking hardware on the Open Compute Project.

Sure, but that's not even close to the "every board and switch is custom designed" story.

there isn't as much exotic "stuff" as you might think. they have the same ODMs build switches and line cards to their specifications, with chips from the same vendors (Broadcom, Cavium, etc) only they can easily hire a team and sign the NDA and write/optimize/perfect the forwarding plane and control plane implementations.

hell, the IS-IS implementation in Quagga is usable because of Google :)

Disclaimer: I'm an SRE at Google, my opinions are my own.

We actually release a decent amount of information, see [0]. I particularly recommend "Jupiter Rising: A Decade of Clos Topologies and Centralized Control in Google's Datacenter Network" [1].

[0] https://research.google.com/pubs/Networking.html [1] https://research.google.com/pubs/archive/46286.pdf