Secondary Storage Media
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Good day friends!
In today's lesson, we will be looking at secondary storage media.
This became necessary due to the fact that primary storage devices such as RAM and ROM are limited in size and are temporary , while secondary storage is permanent and can be used for backup purposes and future use.
A comparison can be made among the variety of secondary storage devices in respect to their portability, speed and capacity.
1.Storage capacity
Storage capacity is the amount that a particular storage medium can hold. Large capacity storage devices are more preferred for many sophisticated programs and large database.
2.Access speed
This refers to the average time needed to locate data on a secondary storage device. Access time is measured in milliseconds.
3.Portability
This refers to the ease and accessibility of a device to transfer information from one computer to another.
For your information, every secondary storage device requires its own drive.Besides,
Storage devices record and retrieve data, instructions and information to and from storage media. Examples are floppy disk drive, hard disk drive, compact disc drive.
Secondary storage devices fall into two main categories:
- Direct Access Storage Devices (DASD)
- Serial/Sequential Access Storage Devices (SASD)
Storage media comprised of many types which is
- Floppy diskettes
- Hard disks
- Magnetic tape
- USB flash drive
- CD-ROM (Compact Disc Read Only Memory)
- WORM (Write Once Read Many)
- Compact Disc Recordable (CD-R)
- Compact Disc Rewritable (CD-RW)
- Digital Versatile/Video Disc (DVD)
- Flash memory
Generally,compact Disc also known as optical disc.The Holographic Versatile Disc (HVD) is an optical disc technology developed between April 2004 and mid-2008 which can store the same amount of information of between 20 and 200 Blu-ray discs.
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| Blu-ray Disc |
A red laser is used as the reference beam to read servo-information from a regular CD-style aluminum layer near the bottom. Servoinformation is used to monitor the position of the read head over the disc, similar to the head, track, and sector information on a conventional hard disk drive. On a CD or DVD.
How Holographic Versatile Discs (HVD) Work?
Holography is a method of recording patterns of light to produce a three-dimensional object. The recorded patterns of light are called a hologram.
HVD offers several advantages over traditional storage technology. First and foremost,HVDs can ultimately store more than 1 terabyte (TB) of information that's 200 times more than a single-sided DVD and 20 times more than a current double-sided Blu-ray.
This is partly due to HVDs storing holograms in overlapping patterns, while a DVD basically stores bits of information side-by-side. HVDs also use a thicker recording layer than DVDs an HVD stores information in almost the entire volume of the disc, instead of just a single, thin layer.
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| Volumetric recording method |
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| DVD vs. HVD: Recording-layer depth |
The other major boost over conventional memory systems is HVD's transfer rate of up to 1 gigabyte (GB) per second that's 40 times faster than DVD.
An HVD stores and retrieves an entire page of data, approximately 60,000 bits of information, in one pulse of light, while a DVD stores and retrieves one bit of data in one pulse of light.
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