This video explains how hard disk drives (HDDs) work and store data. A hard drive contains a metal disk or platter coated with a magnetic material that stores data. The platter is mounted on a spindle and spins at 7200 rpm. A read/write head, attached to an arm, floats 15 nanometers above the disk and reads/writes data by manipulating the magnetic domains on the disk.
The disk is divided into tracks and sectors, with each sector containing a preamble, address, data, error correcting code, and a gap. The read/write head uses a coil of wire to create a magnetic field that magnetizes the domains on the disk, and a multilayer conductive material to detect changes in the magnetic fields.
The video also explores advancements in HDD technology, including the switch to vertical magnetic recording, Shingled Magnetic Recording (SMR), and Heat Assisted Magnetic Recording (HAMR). These advancements have increased the areal density of HDDs, allowing them to store more data in a smaller area.
Additionally, the video mentions the importance of error correcting codes and the use of a DRAM buffer to store data temporarily. It also highlights the role of PCBWay, a sponsor of the video, in providing affordable and high-quality printed circuit boards.
Overall, the video provides a detailed explanation of how hard disk drives work and the technologies that enable them to store large amounts of data.
Here are the key facts extracted from the text:
1. The data stored in a hard disk drive can be incredibly compact, with an entire library worth of books able to fit within the surface of a metal disk.
2. The disk or platter that stores all the data is composed of an aluminum magnesium alloy with multiple coatings of other alloys.
3. The magnetic, functional layer of the disk is a 120-nanometer thin layer of a cobalt chromium tantalum alloy.
4. The platter is mounted on a spindle which spins at a speed of 7200 rpm using a brushless DC motor at its center.
5. The head stack assembly has one arm above and one arm below each disc, with a slider and a read/write head at the end of each arm.
6. The slider uses the airflow generated by the spinning disk to float or fly the read/write head, keeping it only 15 nanometers away from the surface of the disk.
7. The arm assembly is moved by a voice coil motor composed of a coil of wire and two strong neodymium magnets.
8. The read/write head is connected to the outside of the hard drive enclosure and to the printed circuit board (PCB) via a flexible ribbon of wires.
9. The PCB has a main processor, a DRAM chip, and a chip for controlling the voice coil and brushless DC spindle motor.
10. The hard drive has a SATA connector that connects to the motherboard for communications and a separate connector that goes to the power supply.
11. The gasket seals the disk from the exterior environment, and two filters catch any stray dust particles.
12. The read/write heads are only 15 nanometers away from the platter, and a single dust particle can be up to 10,000 nanometers large and cause major damage.
13. The disk is divided into concentric circles of tracks, with the latest hard drives having more than 500,000 tracks on just one side.
14. Each track is divided into sectors, and each sector has a preamble or synchronization zone, an address, actual data, an error correcting code, and a gap between sectors.
15. The read/write head uses a multilayer conductive material with alternating layers of ferromagnetic and non-magnetic materials to detect changes in magnetic fields.
16. The material has a property called giant magnetoresistance (GMR), which changes its resistivity depending on the strength of magnetic fields that pass through it.
17. The read head measures the resistivity to determine the presence or absence of a magnetic field, which corresponds to a 1 or 0.
18. The hard drive uses error correcting codes to ensure that data is accurately written and read.
19. The areal density of hard disk drives has increased by over 50 million times throughout the past 60 years.
20. The cost to store trillions of bits of data has dropped by over 100 million times.
21. Around 2010, the orientation of the domain was switched from being horizontal to vertical, allowing for increased areal density.
22. Shingled Magnetic Recording (SMR) is a technique that allows for increased areal density by writing tracks that partially overlap with previously written tracks.
23. Heat Assisted Magnetic Recording (HAMR) is a technology that uses a small, focused laser to heat the region being written to, making it easier to influence the magnetic region.