What is

Computer data storage?

It is a location where a piece of information can be held temporarily or permanently for use at later. Storage can be of two types: example:

• Internal storage : Hard disk drive
• External/removable storage : Floppy disk, CD-ROM

Computer data storage, often called storage or memory, is a technology consisting of computer components and recording recording media used to retain digital data. It is a core function and fundamental component of computers

_{Types of secondary storges:}

There are several types of secondary storage media used today in the world, each of these can be compared to each other in terms of portability, speed and capacity. Here are discussions on some Secondary Storage Devices:

Magnetic tape:

• Most popular storage medium for large data, which are sequentially accessed and processed.
• Medium is a plastic ribbon.
• Usually ½  inch or ¼ inch wide.
• 50 to 2400 feet long.
• Coated with a magnetisable recording material, such as iron oxide or chromium dioxide.
• Data  recorded in the form of tiny invisible magnetized and non-magnetized spots on the coated surface of the tape.
• The tape ribbon is itself stored in reels or a small cartridge or cassette.
• Like audio or videotape, the magnetic tape used in  computer systems can also 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 Disk:

• Their storage capacity is virtually unlimited.
• With the low cost of tape reels and cartridges, and high data recording densities, the cost per bit of storage is very low for magnetic tapes.
• Since the tape reels and cartridges are compact and light in weight, they are easy to handle and store.
• Due to their compact size and light weight,they are also easily portable from one place to another.

Limitations:

• Due to their sequential access nature, they are not suitable for storage of those data, which frequently require to be accessed randomly.
• They must be stored in a dust-free environment, because specks of dust can cause tape-reading errors.
• They must also be stored in an environment with properly controlled temperature and humidity levels.

They must be properly labled, so that some useful data stored on a tape is not erased by mistake

• For applications, which are based on sequential data processing.
• Backing up of data stored on an on-line storage device,so that , if by accident, the data is corrupted or lost, it can be retrieved from the backup tape.
• Archiving of data which are not used frequently.
• Transferring of data and programs from one computer to another, which are not linked together.

Distribution of software by vendorsUses:

Optic Disk

Optical disk is an electronic data storage medium from which data is read and written to by using a low-powered laser beam. It is flat, circular, plastic or glass disk on which data is stored in the form of light and dark pits.

There are three basic types of optical disks:

 Read-only optical disks, Write once read many Optical disks and Rewritable Optical disks.

Two main types of optical disks are:

-

CD (Compact disk)

1. - is an abbreviation of compact disk, and is a form of data
2. transfer data up to the speed of 7800 KB/s. A standard 120 mm CD holds up to 700 MB of data, or about 70 minutes of audio.

There are two types of CD:

• CD-ROM and CD-RW, CD-ROM are stands for CD-Read Only Memory and they function the same way Read Only Memory Does.
• CD-RW Stards for CD-Rewritable, these disks can be erased and rewritten at any time.

Disavantages of Optic disk:

1. CD-R and DVD-R and DVD+R are 'Write Once, Read Many' formats.  This capability is called "WORM' for short.
2.  We  can only write to the disc once (or in multi-session several times to different locations on the disc before finalizing).
3. Optical discs require special drives to read/write.
4. Optical storage does not provide enough data storage in comparison to other storage technologies

Solid state memory:

A computer memory that is stored within a hardware device that contains no moving parts. For example, Compact Flash memory is commonly a solid-state non-volatile memory.They have high durability,fast boot and portable.

Conpact Flash:

• Short for CompactFlash,
• CompactFlash is a storage medium commonly found in PDAs, Digital Cameras,  portable devices.
• The CF card had a pretty large range of sizes, in terms of storage capacity, ranging from 2MB to 128GB.
• In the picture to the right, is the SanDisk 4.0GB CompactFlash card and an example of what a CompactFlash may look like.

Advantages to Using a Solid State memories

• Solid state drives (SSDs) have many advantages over traditional mechanical HDDs.
• Many of the advantages are a result of SSDs not having any moving parts.
• all the storage on a solid state drive is handled by flash memory chips.R
• Improved Reliability and Durability

• Faster Test Times

Disadvantages of state memories: