Hard drive tracks are really narrow. When you have one head aligned with the track on one platter, the rest of the heads on other platters will only be close to the corresponding tracks on those platters, not fully aligned.
Now that hard drives are using multi-stage actuators (arms with elbows and wrists), it's theoretically possible to align multiple heads to allow writes to be striped across multiple cylinders. But I suspect those advances have instead been used to enable even tighter track spacing (and overlapping, for SMR drives) because SSDs have forced hard drive manufacturers to prioritize density over performance.
I’ve long assumed we got to the point where the surface of the drive was uniform recording material, “tracks” were just the parallel bands the disk made by recording data. There’s difference in the platter material between two tracks, just the gap the heads leave to avoid interference. Conceptually like audio cassette tape: it’s all magnetic, but the audio is stored in separate tracks.
Is that wrong? Is there some physical coating or gap in the recording media between tracks?
If that’s not wrong, wouldn’t always reading/writing the same track across multiple heads force them to stay in alignment?
Now that hard drives are using multi-stage actuators (arms with elbows and wrists), it's theoretically possible to align multiple heads to allow writes to be striped across multiple cylinders. But I suspect those advances have instead been used to enable even tighter track spacing (and overlapping, for SMR drives) because SSDs have forced hard drive manufacturers to prioritize density over performance.