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Computer - Hard Disk Drives (HDD)
What are Hard Disk Drives (HDD)?
The hard disc drive is the main hardware in a computer that stores data. Most files, including the operating system and programme titles, are kept on the hard disc drive.
Components of Hard Disk Drives
A hard drive has a few fundamental elements. One or more shiny silver platters store magnetically stored information, an arm mechanism moves a tiny magnet called a read-write head over the platters to record or store information, and an electronic circuit controls everything and connects the hard drive to your computer.
1. Actuator
The actuator arm is a mechanical element responsible for providing support to the read/write heads. The mechanism facilitates the movement of the read/write heads to the intended track on the platter for data reading or writing. Contemporary hard disc drives (HDDs) employ voice coil actuators to achieve precise positioning.
2. Read-write Heads
Every platter is equipped with a corresponding read/write head that hovers slightly above its surface. These components are tasked with the responsibility of retrieving data from and storing data on the platters. The actuator arm is utilised to swiftly traverse the surface of the platter, facilitating access to various sections of the disc.
3. Central Spindle
Platters rotate at a consistent pace with the spindle. Most HDDs spin at 5,400 or 7,200 RPM, while some high-performance devices spin at 10,000 or 15,000 RPM.
4. Magnetic Platter
it stores information in binary form. The flat, round discs inside an HDD are called platters. Most of the time, these plates are made of aluminium or glass and have a magnetic coating. Magnetic patterns keep the information on the platters.
5. Power Connectors
These link the hard drive to the circuit board in a personal computer. A power connector is needed to power internal HDDs from the computer's power source. Modern discs use SATA power connectors.
6. Read-write Head
The read-write head is a tiny magnet on the end of the read-write arm.
7. Circuit Board
The controller board, also called a "Printed Circuit Board" (PCB), is the HDD's brain. It holds the drive's software, which controls how data is accessed and fixes errors. The drive is also connected to the computer's interface (such as SATA or IDE) by the driver board.
8. Data Connector
The computer's power supply device powers internal HDDs through a power connector. SATA power connectors are common for newer drives.
9. Small Spindle
This allows the read-write arm to swing across the platter. Platters are the most critical hard drive elements. Their name implies that they are hard discs made of glass, ceramic, or aluminium coated with a thin metal coating that may be magnetised or demagnetized. Although compact hard drives have one platter, each side is magnetically coated. Larger drives feature platters stacked on a spindle with a tiny gap. The read-write heads can reach any region of the platters, which rotate at up to 10,000 rpm.
A five-platter hard drive would need ten read-write heads because each platter contains two, one for the top and one for the bottom. An electrically operated arm moves the read-write heads from the drive centre to the edge and back.
Features of Hard Disk Drives
Some of the key features of Hard Disk Drives or HDDs are as follows −
Data Storage
HDDs consist of one or more rigid, rapidly rotating disks (platters) coated with a magnetic material. Data is stored on these platters in the form of magnetic patterns. To read or write data, a read/write head moves over the spinning platters.
Capacity
HDDs are available in various storage capacities, ranging from a few gigabytes (GB) to multiple terabytes (TB). The capacity of an HDD is determined by the number of platters it contains and their data density.
Speed
HDDs are generally slower than SSDs in terms of data access times and read/write speeds. This is because the read/write heads need to physically move to the correct location on the disk, causing latency.
Durability
HDDs are mechanical devices with moving parts, which makes them susceptible to mechanical failure if subjected to physical shocks, drops, or excessive vibration. SSDs, being solid-state, are more durable in this regard.
Price
HDDs are typically less expensive per gigabyte compared to SSDs. This makes them a cost-effective choice for large storage needs.
Noise and Heat
HDDs can generate noise due to the spinning platters and moving heads. They also generate heat, so proper ventilation is necessary to prevent overheating.
Power Consumption
HDDs generally consume more power than SSDs because of the mechanical components. This can lead to slightly higher electricity usage in laptops and desktops.
Longevity
The lifespan of an HDD can vary but is often shorter than that of an SSD. Over time, the mechanical parts can wear out, leading to data loss.
Applications
HDDs are commonly used for various purposes, such as storing large files (photos, videos, and documents), running operating systems and software, and in network-attached storage (NAS) devices for backup and data sharing.
Backup
Due to their mechanical nature, it's important to regularly back up data on HDDs to prevent loss in case of failure. Redundant storage systems or RAID configurations can be used for added data protection.
How do Hard Disk Drives (HDDs) Work?
The working of an HDD depends on its components which are described above. The main elements; a spinning platter and an actuator arm are as −
Magnetic Platters
Platters refer to circular plates. The number of platters in a hard drive is directly proportional to its storage capacity, as each platter can accommodate a specific quantity of information. Consequently, a hard drive with greater storage capacity would include a larger number of platters compared to one with lesser storage capacity. The process of storing and retrieving information from the platters involves the utilisation of concentric circles known as tracks, which are further divided into sectors.
Arm
The arm refers to the component protruding above the platters. The arms are equipped with read and write heads that are utilised to read and store magnetic data onto the platters. Each platter will possess its arm that is utilised to read and write data from and onto it.
The motor is employed to rotate the discs at speeds ranging from 4,500 to 15,000 revolutions per minute (RPM). A higher rotational speed of a drive corresponds to improved performance outcomes. When a computer requires data retrieval from the hard drive, the motor initiates the rotation of the platters, while the arm repositions itself to the designated location above the platter where the data is stored. The magnetic heads located on the arm are responsible for detecting the magnetic bits present on the platters. These heads then convert the detected bits into the corresponding data, which can be utilised by the computer. In contrast, during the process of data transmission to the drive, the magnetic heads will emit magnetic pulses towards the platters, so altering the magnetic characteristics of the platter surface and subsequently storing the information.
HDDs are cheaper and have a higher capacity than SSDs, but they are slower and less durable. The use case and cost-performance-storage capacity balance determine whether to utilise HDDs or SSDs. Computers and electronics store and retrieve data on HDDs. Based on their speed and dependability, Solid State Drives (SSDs) have become popular after decades of use.