The drive case itself didn’t, though. The server, air around the components within its case, the air around the server within the rack, the rack, and the other ferrous materials in the room are what provide enough interference to prevent bit flipping on the disk for the most part. This is assuming a reasonable source of magnetic radiation and not a massive bench power supply on a crash cart powering a rolling EMP. (Of course, I’m being hyperbolic, and it would really just be a more powerful electromagnet and not an EMP)

An electromagnet or even in some cases, a powerful enough rare earth magnet exposed to the drives themselves, or left in proximity to a single computer for an extended period of time can cause destructive data loss to a spinning platter hard disk.