Thrice is a habit - DC migrations
I have just completed my third (actually fourth) data center migration. This, as the saying goes, makes it a habit. The amount of systems varied between a couple of hundreds of websites to more than 1.000 physical servers. As for complexity and stress level, the bandwith was from a smooth, several monthlong process to a hot swap of the complete infrastructure in one night with minimal downtime (the last one, I am still a little shaky).
The DC migration, I have to admit, is my favourite type of project: loads and loads of technical dependencies, techies devouted to their work and their systems and in the end (so far…) happy faces everywhere.