CPU III - Storage Technologies (SS2 FIRST TERM)
Storage Technologies and their Devices
There are basically two types of storage, one is static or non-volatile storage. There are basically three kinds of storage technologies which are:
·
Magnetic Storage
·
Optical Storage
·
Solid State Storage
1.
Magnetic Storage
Magnetic storage encodes data in patterns of positive and negative
magnetic polarity on some magnetic medium like organic metal. Devices like
floppy disks, tape recorder cassettes and Hard disks are all using magnetic
storage technology. Inside hard disks, there are round platters which are made
of metal oxide material and they rotate around the spindle in a high speed.
Similarly they have mechanical part i.e. armature and its head which read/
write the patterns of magnetic polarities on the platters. The patterns are
stored in the form of bits through magnetizing the platters in positive and
negative polarities. The hard disk drives’ storage capacities ranges from
simply Mbs (Mega bytes) to hundreds of TB (Tera-bytes). The inside of hard disk
is shown in the figure below.
Figure:
Inside hard disk
2. Optical Storage
Optical storage technology use laser/optical reflection phenomenon to
read or write data. Two things are required for optical storage technology, one
is the optical media which are circular discs and the other is optical drives
which have the laser beam source for lightening and the photo diodes for
generating the voltages patterns when the reflection beam hit on these.
There are three types of Discs used nowadays
·
CD (Compact Disc) which was firstly discovered
and it is used for storage the music files and some programs. These have low
storage capacity of about 700 MB. These uses the red color laser rays.
·
DVD (Digital versatile Disc): These storing media are used
for storing standard definition movies. These are available in two layers like
DVD-DL (Double Layer). These uses the red color laser rays.
·
BD (Blue-Ray Disc): These are used for storing high
definition movies and these have larger capacities than both the CD and DVD.
These uses the blue color rays laser.
Similarly, these all types of discs have further two categories, one is
ROM (CD-ROM etc.) which are used for permanently storage while the other is RAM
(CD RAM etc.) which can be used for temporary storages like the discs used in
camcorders.
These all disc types can single sided (SS) or Double Sided (DS) as well
as single layer or multi layers.
Following figure shows the above three disc types and notice the
difference in colors.
The other main thing in the optical storage is the optical drives like
CD drive, DVD drive and BD drive. These are also have different categories
which are discussed below
·
Read only Drives: which can only read the discs
but cannot write
·
Write only Drives: Which can only write the discs
but cannot read
·
Read and Write Drives: which can read as well as write
the discs.
Figure:
Optical Drive built in Laptop
3.
Solid State storage
Solid-state storage uses nonvolatile (or flash) memory that can retain
data when power is off. This technology has no moving parts. Solid-state
storage is more expensive but it is lighter, faster, quieter, and more
efficient than the previous ones. Here are the most common forms of solid state
storage:
·
USB flash drive is a stick of highly
portable storage that plugs into a USB port. These are mostly used nowadays
because they have small sizes and good speed.
Figure: USB flash drive
·
Flash memory cards are used in digital
cameras, smartphones, and navigation devices. The most common formats are
CompactFlash, Secure Digital (SD), MemoryStick, and MicroSD.
·
Flash Hard drives also called solid-state
drives (SSDs) are mostly used in the laptops, tablets and many
portable devices. These are same in shapes as the mechanical hard drives but in
smaller size than those. These are mostly used today.
The following figure shows different kinds of solid-state devices.
Figure: Solid-state Devices
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