ICT 0417 - Storage Devices and Media

3. Magnetic Drives

This section focuses on magnetic storage devices, specifically magnetic hard disks and magnetic tape. These devices store data using magnetic fields.

Magnetic Hard Disks (HDDs)

A hard disk drive (HDD) is a non-volatile storage device that uses magnetic storage to store and retrieve digital information. It is a common type of storage found in computers.

How it works

1. The HDD consists of one or more rotating platters coated with a magnetic material.
2. A read/write head, mounted on an arm, moves across the surface of the platters.
3. To write data, the read/write head magnetizes tiny areas on the platter surface, representing bits of data (0s and 1s).
4. To read data, the head detects the magnetic fields on the platter surface and converts them into electrical signals.

Key Features

• Capacity: HDDs typically offer large storage capacities, ranging from hundreds of gigabytes (GB) to several terabytes (TB).
• Speed: Speed is measured in revolutions per minute (RPM). Higher RPM generally means faster data access. Common speeds are 5400 RPM and 7200 RPM.
• Cost: HDDs are generally cost-effective for large storage needs.
• Durability: HDDs are susceptible to damage from physical shock and vibration due to their moving parts.
• Interface: Common interfaces include SATA (Serial ATA) and IDE (Integrated Drive Electronics) (older).

Advantages of HDDs

• High storage capacity
• Relatively low cost per gigabyte

Disadvantages of HDDs

• Slower access times compared to SSDs
• More susceptible to damage from physical shock
• Higher power consumption than SSDs
• Noisier operation due to moving parts

Magnetic Tape

Magnetic tape is a sequential access storage device. Data is written and read in a linear fashion along the tape.

How it works

1. Data is stored on a long, narrow strip of plastic coated with a magnetic material.
2. A read/write head moves along the tape, magnetizing or detecting magnetic patterns to store and retrieve data.
3. Data is written sequentially, meaning that to access a specific piece of data, the tape must be wound or moved to the correct location.

Key Features

• Capacity: Magnetic tape offers very high storage capacities, often in the terabyte range.
• Speed: Data access is slow because of the sequential access method.
• Cost: Tape is relatively inexpensive per gigabyte.
• Durability: Tape can be durable if stored properly in a stable environment.
• Interface: Common interfaces include LTO (Linear Tape-Open).

Advantages of Magnetic Tape

• Very high storage capacity
• Low cost per gigabyte
• Good for long-term data archiving

Disadvantages of Magnetic Tape

• Sequential access makes data retrieval slow
• Requires specialized hardware (tape drives)
• Can be fragile if not handled carefully

Understanding the differences between HDDs and magnetic tape is crucial for choosing the appropriate storage solution for different needs. HDDs are suitable for everyday computing, while magnetic tape is ideal for archiving large amounts of data.