How do Hard Disk Drives Work? 💻💿🛠

Summary

This video script explores the inner workings of a hard disk drive, detailing its components and the process of data storage using magnetic domains. It explains how data is written and read, the advancements in technology that have increased storage capacity, and the future of hard drives with innovations like Shingled Magnetic Recording (SMR) and Heat Assisted Magnetic Recording (HAMR). Sponsored by PCBWay, the script also highlights the importance of reliable printed circuit boards in modern technology.

Takeaways

• 📚 The script describes how data is compactly stored on a hard disk drive, likening it to a single dot of ink from a ballpoint pen.
• 🛠️ The inside of a hard drive contains various components, including a spinning disk (platter) made of an alloy with a thin magnetic layer for data storage.
• 🔍 The read/write head, which floats just 15 nanometers above the disk, is responsible for reading and writing data by manipulating magnetic domains.
• 🔄 The disk spins at 7200 rpm, and the read/write head is moved across the disk by a voice coil motor, allowing for precise positioning.
• 🔗 The data is stored in tracks and sectors on the disk, with each sector containing a preamble, address, data, and error-correcting code (ECC).
• 💾 Writing data involves magnetizing specific regions of the disk, while reading data is done by detecting changes in the magnetic field through giant magnetoresistance (GMR).
• 📈 Advancements in hard disk technology have significantly increased areal density, allowing for more data to be stored in a smaller area.
• 💡 Heat-assisted magnetic recording (HAMR) is a technology that uses a laser to heat the area being written to, enabling smaller magnetic domains and higher storage density.
• 🌐 Shingled Magnetic Recording (SMR) is a technique that allows data tracks to partially overlap, increasing storage capacity but requiring additional read/write steps.
• 🛑 The script mentions the importance of filters to protect the delicate read/write heads from dust particles, which could cause damage due to their proximity to the spinning disk.
• 🔗 The video is sponsored by PCBWay, a company that provides affordable and reliable printed circuit boards and assembly services.

Q & A

How is data compactly stored in a hard disk drive?

Data in a hard disk drive is stored compactly through magnetic domains on the disk's surface. These domains are manipulated using external magnetic fields to represent data, allowing an enormous amount of information to be stored in a very small area, comparable to fitting a year's worth of pictures in a single dot of ink from a ballpoint pen.

What material is the functional layer of a hard disk made of?

The functional layer of a hard disk is a 120-nanometer thin layer made of a cobalt chromium tantalum alloy, which contains small magnetic domains that can be manipulated to store data.

How does the read/write head float above the spinning disk?

The read/write head floats above the spinning disk due to a design feature called the slider, which catches the airflow generated by the fast-spinning disk and uses this airflow to hover the head approximately 15 nanometers away from the disk's surface.

What is the role of the voice coil motor in a hard disk drive?

The voice coil motor, consisting of a coil of wire and neodymium magnets, is used to move the entire arm stack assembly. It controls the exact position of the read/write head by generating a force when electric current is applied, allowing for precise movement across the disk.

How is data written to the hard disk?

Data is written to the hard disk by manipulating the magnetization direction of localized regions or domains on the disk's cobalt-chromium-tantalum layer. A current applied to a coil at the write head creates a magnetic field that aligns the atomic magnetic fields in the domain, effectively writing a bit of data.

How does the read head detect data from the disk?

The read head detects data using a property called giant magnetoresistance (GMR). It measures changes in resistivity caused by magnetic fields from the disk's magnetic domains. A low resistivity indicates a change in domain orientation (binary 1), while high resistivity indicates no change (binary 0).

What is the purpose of the error correcting code (ECC) in a hard disk sector?

The error correcting code (ECC) is used to verify that the data stored in a block is accurately written and properly read. It helps in maintaining data integrity by detecting and correcting common data corruption or loss.

What is the significance of the areal density in hard disk drives?

Areal density refers to the number of bits that can be stored within a given area on the disk. Advances in hard disk technology have significantly increased areal density, allowing for greater storage capacity in the same physical space and reducing the cost of data storage.

What is Shingled Magnetic Recording (SMR) and how does it increase storage capacity?

Shingled Magnetic Recording (SMR) is a technique where data tracks are written to partially overlap with previously written tracks, eliminating guard bands between tracks. This allows for more tracks and data to be stored in a given area, thus increasing the storage capacity of the hard disk.

What is Heat Assisted Magnetic Recording (HAMR) and how does it work?

Heat Assisted Magnetic Recording (HAMR) is a technology that uses a focused laser to heat the region of the disk being written to. This heating makes the magnetic region more easily influenced, allowing for the continued reduction in the size of magnetic domains and thus enabling greater storage density.

Why are filters important in a hard disk drive?

Filters are crucial in hard disk drives because they catch stray dust particles that could potentially collide with the spinning disk. Since the read/write head is only 15 nanometers away from the platter, a dust particle, which can be much larger, could cause significant damage to the drive.

How does the orientation of magnetic domains affect data storage stability?

The orientation of magnetic domains is crucial for data storage stability. Changing the orientation from horizontal to vertical helps in utilizing the depth of the material, making the domains less susceptible to temperature effects and maintaining data integrity over time.