Terravek's second colocation cage, FRA2 in Frankfurt, went into service in 2021 alongside AMS4 in Amsterdam Science Park. We run both with the same small infrastructure team.
The hardware was the easy part. Two cages, comparable specification, diverse transit, site-to-site tunnels, done. Racks B07-01 through B07-06 mirror C12-01 through C12-06 closely enough that a runbook works in either.
The hard part was resisting divergence. A second site attracts exceptions — a slightly newer switch model here, a different firmware baseline there — and every exception doubles the operational surface for a team that did not double in size.
We hold the line with a configuration baseline in version control and a monthly drift report. Anything that differs between sites has to be either fixed or documented as a deliberate exception with an owner. There are currently four exceptions and each has a name against it.
The other thing that helped: physical labelling discipline. Every rack unit, every cable, every port, labelled to the same convention in both cages. It sounds trivial. At 3 a.m. with someone reading a label to you over the phone, it is not.