What will you learn...
Identify the
name of SD
SD Purposes
Characteristics
of SD
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Storage Device
A
storage device is used in the computers to store the data. Its provides
one of the core functions of the modern computer. There is four main types of storage:
Primary
Storage
Secondary
Storage
Tertiary
Storage
Off-Line
Storage
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Primary Storage
Also known as MAIN MEMORY. Main memory is directly or indirectly connected to the central
processing unit via a memory bus. The CPU continuously read instructions stored there and executes them
as required. RAM, ROM and Cache are example of primary storage.
RAM
It
is called Random Access Memory because any of the data in RAM can be accessed
just as fast as any of the other data. Two types of RAM are RAM
(Dynamic
Random Access Memory) and SRAM
(Static Random Access Memory).
STATIC
RAM
Faster
More expensive
More power consumption
does not need to be refreshed
DYNAMIC
RAM
Slower
Less expensive
Less power consumption
needs to be refreshed thousands of times per
second.
This
memory is used as the computer begins to boot up. Small
programs called firmware are often stored in ROM chips on hardware devices
(like a BIOS chip), and they contain instructions the computer can use in
performing some of the most basic operations required to operate hardware
devices. ROM
memory cannot be easily or quickly over written or modified.
CACHE
Cache
is a high-speed access area that can be either a reserved section of main
memory or a storage device. Most
computers today come with L3 cache or L2 cache, while older computers included
only L1cache.
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Secondary Storage
Secondary storage are not directly accessible by the CPU. Computer usually uses its input / output channels to access secondary
storage.Computer usually transfers the desire data using intermediate area in primary storage. Example of secondary storage are hard disk..
HARD DISK
The
hard disk drive is the main, and usually largest, data storage device in a
computer
It
can store any where from 160 gigabytes to 16 terabytes
A
hard disk unit comes with a set rotation speed varying from 4500 to 7200 rpm
Disk
access time is measured in Milli seconds
Internal
Hard Disk
Portability : NO
Portability : NO
Price : LESS EXPENSIVE
Speed : FAST
Size : BIG
Portability : YES
Price : MORE EXPENSIVE
Speed : SLOW
Size : SMALL
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Tertiary Storage
Typically tertiary storage involves a robotic mechanism which will mount (insert) and
dismount removable mass storage media into a storage device. It is a comprehensive computer storage system that is usually very slow. Primarily useful for extraordinary large data stores for example:
Magnetic Tape
Magnetically coated strip of plastic on
which data can be encoded
Less expensive but slower
Example : Cassette Tape
Optical Disk
Holds content in digital format
Read using laser assembly
Example : Blu-ray, CD, DVD
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Off-Line Storage
Also known as disconnected or removable storage. Storage that is NOT under the control of a processing unit. Must inserted or connected by a human operator before a computer can
access it again. Example:
Floppy Disk
A soft magnetic disk
Portable
Can store data up to 1.44MB
Two common size: 5 ¼” and 3 ½”
ZIP Diskette
Developed by Iomega that function like
standard floppy disk
Portable
Hold up to 100MB – 250MB
USB Flash
Drive
A small, portable flash memory card that
plugs into a computer's USB port
Functions as a portable hard drive
Can store data from 256MB to 4TB
Memory Card
Commonly used in consumer electronic
devices such as:
Camera
MP3 Player
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Storage Device Features
Volatility
Volatile:
Require constant power to maintain the stored information
Non
Volatile: Keeps the data even when the current is off
Accessibility
Refers
to reading or writing data records
Random
access: Any location in storage, any time
Sequential
access: Accessing will be in a serial order
Mutability
Allows information to be overwritten at any time
Allows information to be overwritten at any time
Three
types:
Read
Write, Read Only, Slow Write/Fast Read
Addressability
Location-addressable: Stored with numerical memory address
Location-addressable: Stored with numerical memory address
File-addressable:
Stored with human-readable directory
Content-addressable:
Stored based on the basis of contents
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Other Storage Devices
Punched Card
Early method
of data storage
Also known as
Hollerith Cards
Containing
several punched holes that represents data
Cloud Storage
Cloud Storage
The storage of
data online in the cloud
Data can be
stored in and accessible from multiple distributed and connected resources
RAID
Redundant
Array of Independent Disk
Allows us to
store the same data redundantly in a balanced way to improve overall storage
performance
- END OF CHAPTER -
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