CHAPTER 8 (Digital Storage)

CHAPTER 8 Digital Storage 

Storage

Storage is the physical material on which a computer keeps data, information, programs, and applications.

Cloud Storage 

Another storage option, in which the actual online storage media used is transparent to the user.

Access time measures : 

- The amount of time it takes a storage device to locate an item on a storage medium 

- The time required to deliver an item from memory to the processor

Hard Disks

v  A hard disk contains one or more inflexible, circular platters that use magnetic particles to store data, instructions, and information.

The characteristics of a hard disk include :

1)    Bezel

2)    Sealed chamber

3)    Disk platters

4)    Head arm

1)    Head actuator

2)    Drive electronics PCB

3)    Head electronics

4)    Antivibration mount

5)    Read/write head

6)    Mounting chassis

v  Head crash occurs when a read/write head touches the surface of a platter

v  External hard disk is a separate freestanding storage device that connects with a cable to a USB port or other port on a computer or mobile device

Flash Memory Storage

-       Flash memory chips are a type of solid state media and contain no moving parts 

SSD	HDD
High price(1TB≈RM1000)	Low price(1TB≈RM160-200)
Smaller capacity (max1TB lp/4TB pc)	Big capacity (max4TB lp/10TB pc)
Short lifespan	Long lifespan
Low power consumption (2W)	Higher power consumption (7W)
High speed (200-550Mb/s)	Lower speed (50-120Mb/s)

-       Memory card : A removable flash memory device that you insert and remove from a slot in a computer, mobile device, or card reader/writer

-       USB flash drives plug into a USB port on a computer or mobile device

Cloud Storage 

Cloud storage : An Internet service that provides storage to computer  or mobile device users

Optical Discs

Optical disc : consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser

•      Optical discs commonly store items in a single track that spirals from the center of the disc to the edge of the disc

•      Track is divided into evenly sized sectors

     I.        CD-ROM : can be read from but not writable or erasable

   II.        CD-R : an optical disc on which users can write once, but not erase

  III.        CD-RW : an erasable multisession disc

 IV.        DVD-ROM : a high-capacity optical disc on which users can read but not write on or erase

  V.        DVD-R or DVD+R : competing DVD-recordable WORM formats, on which users can write once but not erase

 VI.        DVD-RW, DVD+RW, and DVD+RAM are high-capacity rewritable DVD formats

Other Types Of Storage 

1.    Magnetic stripe card : contains a magnetic stripe that stores information

2.    Smart card : stores data on an integrated circuit embedded in the card

3.    Radio Frequency Identification (RFID tag) : consists of an antenna and a memory chip that contains the information to be transmitted via radio waves

4.    Microfilm and microfiche : store microscopic images of documents on a roll or sheet film