Characteristics, types, and parts of hard disk

A hard disk is the main secondary storage in a computer. They are used to store data, programs, and instructions permanently for later use. The disk is categorized as a magnetic disk storage device because they store data using magnetic technology.

Some types of hard disks are internal or external, PATA, SATA, SCSI, and USB-connected disks. A magnetic hard disk is made up of platters, a read-write head, a sector, tracks, and an actuator among other parts.

opened internal hard disk  showing parts

Characteristics of computer hard drive

  1. Non-volatile: magnetic disk storage is non-volatile which means it stores information permanently even when not powered. They retain data even if the computer power supply is not available.
  2. High storage capacity: Disks can store very high data capacity which can range into Terabytes of data.
  3. Magnetic: disks use magnetic technology to store data. They have magnetic properties that can be magnetized or demagnetized to represent 0 or 1.
  4. Low access speed: compared to RAM and SSD storage hard disks have low access speed and data transfer.

Functions of the magnetic disk 

The main function of a hard disk is to store permanently data and programs in a computer system. The data can be stored for a long time until the user decides to delete it.

Types of computer hard disk

The computer hard disks are categorized into 2 depending on where in the computer it is used from. They can also be classified depending on the types of motherboard connector operation is the same for both categories.

Internal magnetic disk

They are located inside the system unit of the computer hence the name internal. Most computers come with this internal disk install. Depending on the motherboard interface available the disks are connected either using an IDE connector or SATA. IDE was the earlier connector but they are being replaced by SATA which has more advantages. On the computer, the disk is assigned the letter C and it stores the operating system and program files.

Magnetic external disk 

These are the current disks that are mostly used for backup. They are not inside the system unit and they are connected to the computer mostly using USB cables. External disks are also small in size than internal and weigh less. They are designed for portability.

portal Transend external hard disk

Disk drive connector types

Computer hard disks can be categorized using the types of connectors that they use to connect to the motherboard. We discuss the types of connectors that give different types of hard disks.

When it comes to connecting the internal hard drive to the motherboard there are 4 main hard disk interface types used. They are used to move data from the HD to the main memory (RAM) and computer processor. They include

  1. Parallel Advanced Technology Attachment (PATA): they are also known as Integrated  Drive Electronic (IDE). PATA was the initial technology used to connect hard disk drives. They had a data rate of around 133MegaByte/Second.
  2. Serial ATA storage drive: drive connector replaced PATA drives. The types of connection remain the same but data signaling changed from parallel to serial. Data was transmitted one bit at a time and faster than in the PATA. they also have smaller cables and consumed less power.
  3. Small Computer System Interface (SCSI): this connection is meant to connect peripheral devices and it’s faster than the SATA.
  4. Universal Serial Bus (USB): this is the latest type of connector that is replacing others. It is mostly used to connect an external hard disk to the motherboard. Most internal drives are not using a USB for connection.

Magnetic disk storage capacity 

The capacity of the disk or any other storage device is calculated in terms of bytes. Currently, the standard computer has around 1TB of hard disk.

 Since they store data in form of digital, it means it stores as either 0 or 1 (bits). The table below shows how capacity is calculated from the smallest to Petabyte. You can convert different units of storage here.

The number of bytes Storage size
0 OR 1 bit
4bits nibble
8 bits byte
1024bytes 1KiloByte (1KB)
1024KB 1MegaByte (1MB)
1024MB 1GigaByte (1GB)
1024GB 1TeraByte (1TB)
1024TB 1PetaByte (1PT)

Components of magnetic hard disk 

A magnetic disk is made up of disks (platters), the read and writes heads which are held in place by an arm (actuator), and the spindle which holds platters together. The platters are coated with magnetic materials on both sides for data storage. The actuator makes sure that the read and write head moves to the disk location where data need to be read or written to.

labelled parts of hard disk showing spindle, platter, RW head actuator

The platters are divided into tracks and sectors which are used to define a certain location. The more tracks and sectors the higher the disk capacity. Also, the number of platters depends on the intended capacity of the disk. The disk and all other components are enclosed together in a hard drive.

Low-level formatting is done to a new disk to create tracks and sectors to enable the R/W head to write data. The other type of formatting is high-level formatting which is done to the disk that you want to install the operating system.

Parts of a magnetic disk drive

  1. Platter: It is a metallic disk that can be magnetized or demagnetized to read or write data on it.
  2. Tracks: These are concentric circles that run around the surface of the platter
  3. Sector: it is the specific location where data is stored. It is identified by indicating the platter and the track number.
  4. Read/Write head: This is the electronic head that is used to read or write data to the specific sector of the disk.
  5. Spindle: It is the central point where the platter rotates from. It holds platters together to enable them to rotate.
  6. Actuator (Read/write arm): this is the mechanism that holds the head in position.
  7. Cylinder: this is a collection of tracks from different platters that are under the read/write head at a particular time.

Disadvantages of a magnetic disk

  1. It is slow to access data from
  2. It suffers from tear and wears since it has moving parts
  3. It makes noise as it operates
  4. Sit can have bad sectors that cannot store data
  5. It is susceptible to shock if it falls
  6. The disk surface can get damaged.

List of magnetic disk manufacturers

The main manufacturers include

  1. Western Digital Company: It acquired Hitachi Global Storage Technologies (HGST) and which manufactures both internal and external disks. Apart from disk they also support mobile digital lifestyle and other computing technologies.
  2. 2. Fujitsu Incorporation
  3. Seagate Technologies
  4. Quantum Corporation
  5. Toshiba Corporation