Summary
Highlights
Joanne Larson from Seagate introduces two common hard drive form factors: a 2.5-inch drive for notebooks and a 3.5-inch drive. She explains that data is stored magnetically on spinning platters (disks) as 'ones and zeros' or magnetic bits oriented North or South.
Data is written by very small transducers on heads. The 'write pole' focuses magnetic flux to magnetize corresponding areas on the media. The heads 'fly' on a suspension at the end of an arm, part of the head stack assembly (HSA).
The arms move back and forth across the disk to read tracks, which are incredibly narrow, fitting about 300,000 tracks per inch of radius. The HSA pivot is actuated magnetically, using a coil below a magnet, where current creates a magnetic field that moves the coil and thus the arm.
The video shows the motor that spins the media. When the drive is powered off, the heads rest on a ramp, preventing them from touching the media to preserve them. When powered on, the arms swing out, and the heads fly over specific tracks to read or write data.
When a file like a picture is requested, the arms swing to the specific tracks containing the data. The transducer on the head senses the direction of magnetism in tiny magnetic domains, identifying them as ones or zeros. These bits are then transmitted electrically to be reconstructed into the original data.
The video shows the surface of the recording head facing the media. The disk spins underneath, creating an airflow or shear between the air bearing surface and the media. Features on this surface, like airplane wings, control the airflow, ensuring the head flies precisely over the disk.
The visible components of the head only support the transducer, located at the trailing edge where magnetic flux is read and written. A close-up view reveals the transducer's 'write pole' (a tiny dot in a triangle) and the 'read element' (a stripe where the magnetic signal is sensed for reading).
At an 85,000x magnification (with a 200 nanometer micron bar), the layers of the read element are shown to be only a few atoms or molecules thick. This incredibly precise engineering, though conceptually simple, demonstrates an amazing level of technological advancement.