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.
The following table compares and contrasts all the important features of Magnetic Disks and Optical Disks −
ParameterMagnetic DiskOptical DiskMedia TypeMagnetic disk are fixed storage media.Optical disks are portable storage media.Signal To Noise RatioMagnetic disks have intermediate S/N ratioOptical disks have excellent S/N ratio.Sampling RateThe sampling rate of magnetic disks is low.The sampling rate of optical disks is high.UsageMagnetic disks are commonly used where random access is needed.Optical disks are used where a regular data streaming is needed.Track StructureMagnetic disks have circular track structure.Optical disks have spiral track structure.Data AccessHard Disk, Floppy Disk, Magnetic Tape, etc. are examples of magnetic disksCD, DVD, Blu-ray, etc., are the examples of optical disks.ReuseMagnetic disks are highly reusable and used for random read/write operations.Most of the optical disks are readonly once written.CostMagnetic disks are costly per MB.Optical disks are cheaper per MB.Conclusion
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.
If you are unable to see the table.Then, copy it and paste it into microsoft word.
Magnetic Storage
Optical Storage
a] Stores data in magnetic form.
b] It is affected by magnetic field.
c] It has high storage capacity.
e] It doesn't use laser to read/write data.
f] Magnetic storage devices are ; Hard disk , Floppy
disk, Magnetic tape etc.
a] Stores data optically & used laser to read/write.
b] It is not affected by magnetic field.
c] It has less storage than hard disk.
e] Data accessing is high as compared to floppy.
f] Optical storage devices are ; CD-ROM,CD-R,
CD-RW, DVD etc.
Optical Storages used to be incredibly popular up until the last couple of years where cloud storage and the rise of video and game streaming services have massively reduced their popularity.
Types of optical storage devices:
- CD Drives [700MB]
- DVD Drives [4.7GB]
- BluRay Drives [50GB]
Optical storage devices offer cheap and portable high capacity secondary storage. Far more portable than an internal hard-drive, which makes them good for small / medium size backups and great for sending through the post.
How they work
Optical storage devices work by firing a laser at the surface of a spinning disk. The disc is covered in a pattern of pits in the CD surface. As the laser hits the pits it is reflected and the pattern of pits it detected by a laser detector.
Solid State Storage
Solid State Storage Devices
SSD Drive – Expensive but fast
Solid-State-Devices-Revision-Sheet
Solid state devices are the newest form of storage to emerge. The technology is used in Hard Drives, SD Cards and USB sticks. Solid state storage devices work by storing data in flash chips electronically. They are still more expensive than traditional storage devices but the price per GB is falling all the time.
Advantages
- Very fast read / write speeds.
- Shock resistant as there are no moving parts to break if knocked
- No moving parts so longer battery life [ great for laptops / tablets / smartphones]
Disadvantages
- More expensive per GB of storage
- Limited life span, as each flash cell can only be written to a limited number of times.
Very portable and small – but needs a reader to use