The hum that never stops

Sometimes at 3 AM I stand in the aisle and the servers sound like they're breathing—not just cooling fans, but a slow tide. I started noticing cables that weren't in the diagrams, running between racks that aren't supposed to talk to each other. They hum a note that's a little off from the rest, and I think maybe the datacenter has its own kind of ghost, something that persists because we forgot to label it.