What are magnetic storage systems ? Describe magnetic tapes and magnetic disks with their relative advantages and disadvantages.Ripunjay Tiwari
Ans. Magnetic storage systems are defined as the storage systems that store the data on a magnetized medium with the help of magnetized particles. Examples of magnetic storage systems are magnetic tapes, magnetic disks, hard disks, floppy disks. The magnetic storage systems are non-volatile and provide the facility to store data. Data can be accessed randomly as well as sequentially. When data is accessed sequentially, the access time is directly proportional to the searching point. That is , the searching point is near, the access time is less, and if the searching point is far, then the access time is more. In contrast, when data is accessed randomly, the access time is less.
Magnetic Tapes – It is a mass storage device, and used as a backup storage. Magnetic tape is one of the most popular storage medium for large data, that are sequentially accessed and processed. The tape is a ribbon of mylar (a plastic like magnetic) usually ½ inch wide that is coated on one side with an iron-oxide material which can be magnetized. The tape ribbon itself is stored in reels of 50 to 2400 feet or a small cartridge or cassette. It is similar to the tape used on a tape recorder, except that it is of higher quality and is more durable. Like recorder tape, computer tape can be erased and reused indefinitely. Old data on a tape are automatically erased as new data are recorded, in the same area.
Advantages of Magnetic Tape-
- Unlimited Storage – The storage capacity of a magnetic tape is virtually unlimited because we can use as many tapes as required for recording our data.
- High Data Density – A typical 10.5 inch reel of magnetic tape is 2,400 feet long and is able to hold 800, 1600 or 6250 characters per inch of this length.
- Portability – A reel of tape is also a convenient way of carrying information from one place to another. It is often used for transformation from one place to another.
- Low Cost – Cost of magnetic tape is much less as compared to other data storage devices. An additional cost benefit is that, tapes can be erased and reused many times.
- Rapid Transfer Rate – Data transfer rate for a magnetic tape can be in excess of 1 million bytes per second.
- Ease of Handling – It takes much less storage space and much easier to handle.
Limitations of Magnetic Tape-
- No Direct Access – Magnetic tape is a sequential access device hence data recorded on tape cannot be addressed directly. They can only be retrieved serially.
- Indirect Interpretation – Data stored on a magnetic tape are in the form of tiny invisible magnetized and non-magnetized spots. Hence, the contents of a tape cannot be interpreted and verified directly.
- Environmental Problem – Specks of dust and uncontrolled hu8midity or temperature levels can cause tape reading errors. Tapes and reel containers must be stored in a dust free environment.
Magnetic Disks – It is a flat disk that is covered with magnetic coating for holding information. It is a type of secondary memory device that is used to store different programs and files. It stores information in the form of small and magnetized needles. These needles helps in encoding a single bit of information by getting polarized in one direction represented by 1, and opposite direction represented by 0.
Magnetic disk can store a large amount of data and is less expensive than RAM. Its data access rate is slow as compared to the main memory. It allows the random access of data and provides the facility of erasing and re-recording the data as many times as needed. Fig. 1.18 shows a magnetic disk with sectors and tracks.