What is Storage Device?
Storage Devices are the data storage
devices that are used in the computers to
store the data.
The computer has many types of data
Some of them can be classified as the
removable data Storage Devices and the
others as the non removable data Storage
The memory is of two types:
One is the Primary Memory and the other one is
the Secondary Memory.
The primary memory is the volatile memory (RAM)and
the secondary memory is the non volatile memory.
The volatile memory is the kind of the memory that is
erasable and the non volatile memory is the one where
in the contents cannot be erased. Basically when we talk
about the data storage devices it is generally assumed to
be the secondary memory.
What are the Secondary
The Secondary Memory is used to store the data
permanently in the computer.
The secondary storage devices are usually as
hard disk drives – this is the most common type
of storage device that is used in almost all the
The other ones include the floppy disk drives,
the CD ROM, and the DVD ROM. The flash
memory, the USB data card etc.
Magnetic tape has been used for data storage for over 50
years. When storing large amounts of data, tape can be
substantially less expensive than disk or other data
This medium consisting of a thin tape with a coating of a
fine magnetic material, used for recording analogue or
A device that stores computer data on magnetic tape is a
tape drive. The capacity of tape media are generally on
the same order as hard disk drives (The largest being
about 5 Terabytes in 2011).
Magnetic Tapes Generally transfer data a bit slower than
hard drives, however magnetic tapes are cheaper and are
• Writing and retrieving data is slow.
It uses serial access for reading and writing.
• Magnetic tapes are used for application which
requires extremely large storage capacity where
speed of access is not an issue.
It is commonly used for backups of file servers
for computer networks, in a variety of batch
processing applications such as reading of bank
cheques, payroll processing and general stock
Floppy Disks were an were a ubiquitous form of data
storage between 1980's and early 2000's,
Floppy disks comes in 3 sizes: 8-inches, 5.5-inches and
The capacities of Floppy disks vary between 1-2.50
Megabytes and these devices were very slow, reading
data at rates of bytes and Kbytes/second. However,
most are very small and portable.
• Any use where small files such as word processing,
small spreadsheets and databases need to be moved
from one computer to another.
Useful to backup small data files.
Fixed Hard Discs
A hard disk drive is the device used to store large
amounts of digital information in computers.
Hard disk drives are used to store operating
systems, software, video, music and working data.
These are suitable for any application which
requires very fast access to data for both reading
and writing to.
Almost all computers used a fixed hard disc. Used
for on-line and real time processes requiring direct
Used in file servers for computer networks to store
large amount of data.
It is a non-volatile, random access digital magnetic
data storage device.
A hard drive is made up of platters which stored the
data, and read/write heads to transfer data.
A Hard Drive is generally the fastest of the
secondary storage devices, and has the largest data
storage capacity, approximately the same as
Hard drives however, are not very portable and are
primarily used internally in a computer system.
Some persons use hard drives externally as a form
of storage and as a substitute for portable storage,
hard drives used for these purposes are called
external hard drives.
Portable Hard Discs
Portable hard discs are good fun because you
can carry data about all over the place and
transfer information, programs, pictures, etc.
This hardware can be connected with laptop,
notebook and pc using USB port.
Plug and play enable the device more flexible to
We can carry any where else due to its smaller
size, price and capacity.
• Greatly improved data cargo carrying capacity
(relative to the 1.44 Mb floppy disc).
• Hard drives have to be handled quite carefully, and
when being transported should be wrapped in
something soft and put in a padded bag.
• More expensive than other forms of removable
• Portable disc discs are used to store very large files
which need transporting from one computer to
another and price is not an issue.
Optical backing storage media such as
CDs and DVDs
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 and DVD
It is an abbreviation of Digital Versatile Disc, and is
an optical disc storage media format that can be
used for data storage. The DVD supports disks with
capacities of 4.7 GB to 17 GB and access rates of
600 Kbps to 1.3 Mbps.
A standard DVD disc store up to 4.7 GB of data.
There are two types of DVD's:
DVD-ROM and DVD-RW.
DVD-ROM are stands for DVD-Read Only
Memory and they function the same way Read Only
Memory Does. DVD-RW Stands for DVD-Rewritable,
these disks can be erased and rewritten
at any time.
Flash Drive – Pen drive
A Flash drive is a small external storage device,
typically the size of a human thumb that consists of
USB flash drives are removable and rewritable
reads and writes to flash memory.
They are a solid-state storage medium that's both
inexpensive and durable.
Currently, USB 2.0 flash drives on the market are
able to reach a data transfer speed of 480 Mbit/s
USB 3.0 has transmission speeds of up to 5 Gbit/s.
USB Flash drives vary in sizes from 128 Megabytes
to 64 Gigabytes. More commonly used sizes vary
from 2 Gigabytes -16 Gigabytes.
Flash Memory cards
Flash memory is a EEPROM non-volatile
computer storage chip.
These Memory cards currently vary in sizes
between 1 Gigabytes -16 Gigabytes and they
transfer data at a rate of approximately 14.65
Inexpensive and durable, and are very small.
It has a size of about 1 inch * 0.75 inch with a
thickness of about 2mm.
Flash memory cards also have a smaller version
which is used within cell phones, digital camera,
Tablet Pc etc.,
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