Primary memory has limited storage capacity and is volatile. Secondary memory overcome this limitation by providing permanent storage of data and in bulk quantity. Secondary memory is also termed as external memory and refers to the various storage media on which a computer can store data and programs. The Secondary storage media can be fixed or removable. Fixed Storage media is an internal storage medium like hard disk that is fixed inside the computer. Storage medium that are portable and can be taken outside the computer are termed as removable storage media.
Difference between Primary Memory and Secondary Memory:
Uses of Secondary Media:
A Fixed storage is an internal media device that is used by a computer system to store data, and usually these are referred to as the Fixed Disks drives or the Hard Drives.
Fixed storage devices are literally not fixed, obviously these can be removed from the system for repairing work, maintenance purpose, and also for upgrade etc. But in general, this can’t be done without a proper toolkit to open up the computer system to provide physical access, and that needs to be done by an engineer.
Technically, almost all of the data i.e. being processed on a computer system is stored on some type of a built-in fixed storage device.
Types of fixed storage:
A Removable storage is an external media device that is used by a computer system to store data, and usually these are referred to as the Removable Disks drives or the External Drives.
Removable storage is any type of storage device that can be removed/ejected from a computer system while the system is running. Examples of external devices include CDs, DVDs and Blu-Ray disk drives, as well as diskettes and USB drives. Removable storage makes it easier for a user to transfer data from one computer system to another.
In a storage factors, the main benefit of removable disks is that they can provide the fast data transfer rates associated with storage area networks (SANs)
Types of Removable Storage:
There are the following main types of storage media:
1. Magnetic storage media
Magnetic media is coated with a magnetic layer which is magnetized in clockwise or anticlockwise directions. When the disk moves, the head interprets the data stored at a specific location in binary 1s and 0s at reading.
Examples: hard disks, floppy disks and magnetic tapes.
Hard disk drive components: Most of the basic types of hard drives contains a number of disk platters that are placed around a spindle which is placed inside a sealed chamber. The chamber also includes read/write head and motors. Data is stored on each of these disks in the arrangement of concentric circles called tracks which are divided further into sectors. Though internal Hard drives are not very portable and used internally in a computer system, external hard disks can be used as a substitute for portable storage. Hard disks can store data upto several terabytes.
2. Optical storage media
In optical storage media information is stored and read using a laser beam. The data is stored as a spiral pattern of pits and ridges denoting binary 0 and binary 1.
Examples: CDs and DVDs
3. Solid State Memories
Solid-state storage devices are based on electronic circuits with no moving parts like the reels of tape, spinning discs etc. Solid-state storage devices use special memories called flash memory to store data. Solid state drive (or flash memory) is used mainly in digital cameras, pen drives or USB flash drives.
Pen Drives or Thumb drives or Flash drives are the recently emerged portable storage media. It is an EEPROM based flash memory which can be repeatedly erased and written using electric signals. This memory is accompanied with a USB connector which enables the pen drive to connect to the computer. They have a capacity smaller than a hard disk but greater than a CD. Pen drive has following advantages: