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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

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