Difference between Magnetic Disk and Optical Disk

In a computer system, several types of secondary storage devices like HDD, CD, DVD, etc. are used to store permanent data and information. These devices can be categorized into two types namely – magnetic memory and optical memory.

A magnetic memory like HDD consists of circular disks made up of non-magnetic materials and coated with a thin layer of magnetic material in which data is stored. On the other hand, optical disks are made up of plastic and consist of layers of photo-sensitive materials in which the data is stored using optical effects. A major advantage of the magnetic disk and optical disk is that they are inexpensive storage devices.

What is a Magnetic Disk?

A Magnetic Disk is a storage device and uses magnetization process for data processing like read/write/access operations.

Magnetic disks have circular platters coated with magnetic material. The platters are made up of non-magnetic materials like aluminium and its alloys. These disks are placed inside a rotary drive where the magnetized surface of the disk rotates close to read-write head, where the read-write head is a device consists of a magnetizing coil and a magnetic yoke. The readwrite head produces a magnetic field based on instruction to store or delete the data on the disk. Data is stored in form of tracks, spots and sectors.

Examples of Magnetic disks include hard disks, floppy disks, magnetic tapes, etc.

What is an Optical Disk?

Optical Disk is again a storage device and use optical storage technology for data processing like read/write/access operations. An optical disk stores data using laser light and is read using the same. Laser light reads data on a spinning disk.

Optical disks are also used as the permanent storage device in computers. An optical disk is made up of a resin like polycarbonate, and the digital data and information is stored in the polycarbonate surface in the form of microscopic pits. Then, the microscopic pitted surface is polished with a highly reflective substance. Also, in order to protect the disk from scratches, it is coated by acrylic. The data is read and write on the disk through a low-powered laser beam housed in an optical disk player.

Examples of optical disks include CD, DVD, Blue Ray Disk, etc.

Difference between Magnetic Disk and Optical Disk

The following table compares and contrasts all the important features of Magnetic Disks and Optical Disks −

Parameter Magnetic Disk Optical Disk
Media Type Magnetic disk are fixed storage media. Optical disks are portable storage media.
Signal To Noise Ratio Magnetic disks have intermediate S/N ratio Optical disks have excellent S/N ratio.
Sampling Rate The sampling rate of magnetic disks is low. The sampling rate of optical disks is high.
Usage Magnetic disks are commonly used where random access is needed. Optical disks are used where a regular data streaming is needed.
Track Structure Magnetic disks have circular track structure. Optical disks have spiral track structure.
Data Access Hard Disk, Floppy Disk, Magnetic Tape, etc. are examples of magnetic disks CD, DVD, Blu-ray, etc., are the examples of optical disks.
Reuse Magnetic disks are highly reusable and used for random read/write operations. Most of the optical disks are readonly once written.
Cost Magnetic disks are costly per MB. Optical disks are cheaper per MB.


The most significant difference between a Magnetic Disk and an Optical Disk is that a magnetic disk stores the data using magnetic field, while an optical disk uses photo-sensitive materials and effects of light (laser light) to store the data.

Updated on: 24-Nov-2022

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