Secondary Storage

Secondary Memory Secondary memory, also known as storage, refers to non-volatile memory external to the computer. It is employed for storing large amounts of data, for permanent or long-term storage of data or programs, and for creating backups.   Secondary storage media can be categorized based on the following criteria: (i) Retrieval speed: The time […]

Secondary Memory

Secondary memory, also known as storage, refers to non-volatile memory external to the computer. It is employed for storing large amounts of data, for permanent or long-term storage of data or programs, and for creating backups.

 

Secondary storage media can be categorized based on the following criteria:

(i) Retrieval speed: The time taken to locate and retrieve stored data.

(ii) Size/Storage capacity: The ability to store data, with a preference for large storage capacity.

(iii) Cost per bit of capacity: Preference for low cost.

 

Types Of Secondary Memory

(i) Magnetic Disk: This consists of a Mylar or metallic platter where electronic data are stored. Data are recorded as tiny magnetic spots on its iron oxide coating. Access time is determined by seek time (positioning the read/write head over the paper track) and search time (spinning the required data under the head). Once accessed, data are transferred from the disk to the processor for processing. The transfer rate depends on data density and disk rotational speed.

 

Magnetic Disks come in two categories:

(a) Fixed disk or Hard disk: Made from materials like aluminum instead of Mylar, it may be permanently installed or in the form of a removable disk.

 

Forms of Fixed disk or hard disk:

  1. Larger permanent sealed metal disk (14-inch) used in larger systems and minicomputers.
  2. Larger metal disk in removable cartridges (14-inch) used in mini-sized and larger systems.
  3. Rigid disks permanently housed in Winchester drives, available in 9, 8, and 5¼ inches sizes.
  4. 3½ inch disks currently used in PCs, servers, and smaller ones in notebooks and other devices.

 

(b) Floppy Disk: Available in three sizes:

  1. 8-inch portable floppy (flexible) disk.
  2. 5¼-inch portable floppy disks.
  3. Compact floppy disk measuring less than 4 inches in diameter.

 

Optical Technology Storage

This involves the use of laser beams, highly concentrated beams of light, in the form of:

(a) Optical laser disk, including Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), Digital Versatile Disk (DVD), or flash. Data stored can be read by CD-ROM drives, CD-RW drives, DVD-ROM drives, DVD-RW drives, or flash drives.

 

(b) DVD drive: A Digital Versatile Disk (DVD) is similar to a CD but has a much larger data capacity, consisting of several layers of plastic totaling about 1.2 millimeters thick. DVDs have various types and formats similar to CDs.

 

Flash Drives

These small devices facilitate easy file transportation and usage. Plug-and-play pen drives come in capacities ranging from 16 MB to 1 GB, offering faster and more reliable performance than floppy disks.

 

Comparison of Memory devices:

The characteristics of different data storage types in the storage hierarchy are summarized below:

Registers:

    1. Speed: Registers are the fastest form of storage, providing nearly instantaneous access to data.
    2. Capacity: Limited capacity, typically used for storing small amounts of critical data.
    3. Relative Costs: Registers are the most expensive form of storage due to their speed and low capacity.
    4. Permanent?: Data is not permanent in registers, as they are volatile and lose content when power is turned off.

 

RAM (Random Access Memory):

  1. Speed: Very fast access to data, making it suitable for actively running programs.
  2. Capacity: Moderately low capacity, used for temporary storage during active tasks.
  3. Relative Costs: Relatively high costs compared to other storage types due to speed and volatility.
  4. Permanent?:* Data is not permanent in RAM, as it is volatile and erased when the power is lost.

 

SSD (Solid State Drive):

  1. Speed: Fast access to data, falling between RAM and HDD.
  2. Capacity: Moderate to high capacity, making it suitable for various applications.
  3. Relative Costs: Moderate costs compared to the high speed and capacity offered.
  4. Permanent?: Data stored on an SSD is considered permanent, as it retains information even without power.

 

HDD (Hard Disk Drive):

  1. Speed: Moderate access speed, slower than SSD but with higher capacity.
  2. Capacity: Very high capacity, commonly used for long-term storage of large amounts of data.
  3. Relative Costs: Low relative costs compared to the high capacity offered.
  4. Permanent?: Data on an HDD is considered permanent, as it retains information even when powered off.

 

Floppy Disk:

  1. Speed: Very slow access speed, primarily used in older computer systems.
  2. Capacity: Low capacity, suitable for small files and documents.
  3. Relative Costs: Low costs due to slow speed and limited capacity.
  4. Permanent?: Data on a floppy disk is considered permanent, as it retains information even without power.

 

CD/DVD:

  1. Speed: Slow access speed, used primarily for archival purposes.
  2. Capacity: Moderate capacity, often used for distributing software and multimedia content.
  3. Relative Costs: Low costs compared to the storage capacity offered.
  4. Permanent?: Data on a CD/DVD is considered permanent, as it retains information even without power.

Related Posts:

Memory Unit

Central Processing Unit (CPU)

Overview Of Computer Hardware

Presentation Package | Examples, Features, Creation of Slides & Animation

Word Processor

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top