Storage device

• Data drives provide non-volatile storage of data.

• A storage device is any hardware capable of holding information so storage in
the computers process of retaining information for future use.
• Designed to permanently store user data, user applications and the operating
System.
• It Can be internal or external to the computer.
• Some drives have fixed media, and other drives have removable media.
• Data storage devices can be classified according to the media on which the data
is stored:
• Magnetic – like hard disk drive and tape drive
• Solid state – like solid state drive
• Optical – like CD and DVD
2
 The floppy drive

• A floppy disk is a portable computer storage

device that permits easy handling of data.
• It is commonly used with personal
computers, notebook computers and word
processors.
• Such disks consist of flat, circular plates
made of metal or plastic and coated with
iron oxide.
• Information can be magnetically imprinted
on this coating
• It needs floppy disk drive to use
3
Cont..

• Three different generations of floppy

disks: 8-inch, 5.25-inch and 3.5-inch
were available in the market.
• The first floppy disk that come on the
market were 8-inches (20cm) in diameter.
• The most common 8-inch disks size are
360KB and 1.2MB.

4
 Magnetic Media Storage
This type of storage represents binary values as
magnetized or non magnetized physical areas of magnetic
media.
Common types of magnetic media storage drives:
• Hard Disk Drive (HDD) – the traditional magnetic
disk devices with storage capacity ranging from
gigabytes (GBs) to terabytes (TBs).
• Magnetic hard drives have drive motors designed to
spin magnetic platters and move the drive heads.
• Speed is measured in revolutions per minute.
– Common speeds are 5400rpm, 7200rpm, 10,000rpm.

5
 Magnetic Media Storage
[Basic Components of hard disk]
• Platters are rigid disks made of metal or plastic.
• Both sides of each platter are covered with an
extremely thin coating of iron oxide or other
magnetizable material.
• The platters are mounted on a central axle or
spindle, which rotates all the platters at the same
speed.
• Read/write heads are mounted on head arms
that extend over both top and bottom surfaces
of each disk.
• There is at least one read/write head for each
side of each platter. 6
 Magnetic Media Storage
[Basic Components of hard disk..]
• The arms jointly move back and forth between
the platters’ centers and outside edges; this
movement, along with the platters’ rotation,
allow the read/write heads to access all areas of
the platters.
• The integrated electronics translate
commands from the computer and move the
read/write heads to specific areas of the
platters, thus reading and/or writing the needed
data.
• The head actuator is the device used to
position the head arms to different tracks on
the surface of the platter 7
 Magnetic Media Storage
[Basic Components of hard disk..]
Tracks and Sectors:
• Platters are organized into specific structures to
enable the organized storage and retrieval of data.
• Each platter is broken into tracks- tens of
thousands of them - which are tightly-packed
concentric circles.
• Each track is further broken down into sectors.
• A sector is normally the smallest individually-
addressable unit of information stored on a hard
disk, and normally holds 512 bytes of
information.
8
 Magnetic Media Storage
Common types of magnetic media storage drives:
• Tape Drive – most often used for archiving data.
– Tape drives use a magnetic read/write head and
removable tape cartridge.
– Common tape storage capacities vary between a
few GBs to many TBs.

• A floppy disk drive (FDD) is storage device that uses

removable 3.5 inch floppy disks that can store up to
1.44 MB of data.

9
 Semiconductor Storage
1. Solid-state drives (SSD) store data as electrical charges in
semiconductor flash memory. This results in faster access to data, improved
performance, higher reliability, reduced power usage.
• SSDs have no moving parts, make no noise, are more energy efficient,
not susceptible to vibrations, and produce less heat than HDDs.
• SSD storage capacity ranges from around 120 GBs to many
TBs.
• SSDs come in three form factors:
• Disc drive form factor – similar to an HDD
• Expansion cards – plugs directly into the
motherboard and mounts in the computer case like other
expansion cards
• mSata or M.2 modules – these packages may use
a special socket.
10
– M.2 is a standard for computer expansion cards.
 Semiconductor Storage
2. Solid State Hybrid Drives (SSHDs) are a compromise between a
magnetic HDD and an SSD.
• They are faster than an HDD but less expensive than an SSD.
• They combine a magnetic HDD with onboard flash memory serving as
a non-volatile cache.
3. A flash drive is a removable storage device that connects to a USB port.
A flash drive requires no power to maintain the data.
• it supports up to 1TB

11
 Optical Storage Devices
Types of Optical Storage Device:
❑ Optical drives are removable media storage devices that
use lasers to read and write data on optical media.
❑ They were developed to overcome the storage capacity
limitations of removable magnetic media such as floppy
discs.
❑ There are three types of optical drives:
1. Compact Disc (CD) - audio and data
2. Digital Versatile Disc (DVD) - digital video and data
3. Blu-ray Disc (BD) - HD digital video and data

12
❑ CD, DVD, and BD media can be pre-recorded (read only), recordable (write once), or re-
recordable (read and write multiple times).
DVD and BD media can also be single layer (SL) or dual layer (DL). Dual layer media
roughly doubles the capacity of a single disc.

13
 How Is Data Stored and Retrieved?

• When a computer saves data, it sends the data to the hard disk as a series of
bits( 0s and 1s).
• As the disk receives the bits, it uses the read/write heads to magnetically record
or “write” the bits as a magnetic charge on the oxide coating of a disk platter.
• NB: Data bits are not necessarily(but it is possible) stored in succession;
• For example, the data in one file may be written to several different
areas on different platters.
• When the computer requests data stored on the disk, the platters rotate and the
read/write heads move back and forth to the specified data areas.
• The read/write heads read the data by determining the magnetic field of each
bit, positive or negative, and then reply that information back to the computer.
14
 Disk Formatting
• Disk formatting is the process of preparing a data storage device such as a hard
disk drive, solid-state drive, floppy disk, memory card or USB flash drive for
initial use.
• Formatting prepares the hard disk so that files can be written to the platters and
then quickly retrieved when needed.
• Hard disks must be formatted in two ways: physically and logically
• A hard disk’s physical formatting (also called low-level formatting) is usually
performed by the manufacturer. (means when they are built)
• Physical formatting divides the hard disk’s platters into their basic physical
elements: tracks, sectors, and cylinders

15
• The tracks are identified by number, starting with track zero at the
outer edge.
• A cylinder is comprised of a set of tracks that lie at the same distance
from the spindle on all sides of all the platters.
16
• Computer hardware and software frequently work using cylinders.

• Bad sectors: Are the sectors that can no longer be used to hold data due to
gradual deterioration of magnetic properties of the platter coating.

• Consequently, it becomes more and more difficult for the read/write heads to
read data from or write data to the affected platter sectors

• Most modern computers can determine when a sector is bad; if this happens,
the computer simply marks the sector as bad (so it will never be used) and
then uses an alternate sector. 17
18
 Logical Formatting

• After a hard disk has been physically formatted, it must also be logically
formatted.
• Logical formatting refers to the process of preparing a storage medium,
usually a disk, for data storage in accordance with a certain file system
structure.
• Logical formatting places a file system on the disk, allowing an
operating system (such as DOS, OS/2, Windows, or Linux) to use the
available disk space to store and retrieve files.

19
 Understanding Partitions

• After a disk has been physically formatted, it can be divided into separate
physical sections or partitions.
• Each partition functions as an individual unit, and can be logically
formatted with any desired file system.
• Once a disk partition has been logically formatted, it is referred to as a
volume.
• As part of the formatting operation, you are asked to give the partition a
name, called the “volume label.”
• This name helps you easily identify the volume

20
 Why Use Multiple Partitions?

• Install more than one OS on your hard disk;

• Make the most efficient use of your available disk space;

• Make your files as secure as possible;

• Physically separate data so that it is easy to find files and back up data.

21
 Partition types
• There are three kinds of partitions:
1) primary,
2) extended, and
3) logical.
• Primary and extended partitions are the main disk divisions
• One hard disk may contain up to four primary partitions, or three
primary partitions and one extended partition.
• The extended partition can then be further divided into any number of
logical partitions

22
 1) Primary partition:
• A primary partition may contain an operating system along with any number of data files
(for example, program files or user files). Before an OS is installed,
• The primary partition must be logically formatted with a file system compatible to the OS.
• If you have multiple primary partitions on your hard disk, only one primary partition may
be visible and active at a time.
• The active partition is the partition from which an OS is booted at computer startup.
• Primary partitions other than the active partition are hidden, preventing their data from being
accessed.
• Thus, the data in a primary partition can be accessed (for all practical purposes) only by the
OS installed on that partition
23
2) Extended partition:
• The extended partition was invented as a way of getting around the
arbitrary four-partition limit.
• An extended partition is essentially a container in which you can further
physically divide your disk space by creating an unlimited number of logical
partitions.
• An extended partition does not directly hold data. You must create logical
partitions within the extended partition in order to store data.
• Once created, logical partitions must be logically formatted, but each can use
a different file system.
24
 3) Logical partitions:

• Logical partitions can exist only within an extended partition

and are meant to contain only data files and OSs that can be
booted from a logical partition (OS/2, Linux, and Windows
NT)
• You can access logical partition files from multiple OSs

25
26
 Managing Partitions
• Shrinking volume
• Extending volume
• Creating partition
• Deleting volume
• Hiding volume
• Making primary part as active

27
• When you create multiple primary partitions to hold different operating
systems, you must tell the computer which primary partition to boot from.
• The primary partition from which the computer boots is called the active
partition.
• If there is not an active primary partition on the first physical hard disk,
your computer will not be able to boot from your hard disk.
• WARNING! Before you make a primary partition active, make sure that it
is a bootable partition.
• Bootable partitions are logically formatted and have the necessary OS files
installed.
• Partitions without an OS cannot be booted. 28
 Head Crashes

• Read/write heads of a hard disk are floating on a microscopic layer

of air above the disk platters
• Normally, the heads only contact the surface when the drive is
either starting up or stopping.
• It is possible that the heads can make contact with the media
• Head crash is a condition where the heads contact the surface of
the disk while it is at operational speed.

29
 Head Crashes
• The most common causes of head crashes are contamination getting stuck in
the thin gap between the head and the disk, and shock applied to the hard disk
while it is in operation.

30
 Hard disk drives Vs Solid state drives
• Solid state drives (SSDs) do not have moving parts, which results in faster
access to data, higher reliability, and reduced power usage.
• It uses flash memory to store data

• SSDs can replace HDD soon

31
 SSD vs HDD cont…
Solid State Drive(SSD) Hard Disk Drive(HDD)
Access speeds of 35 to 100 micro- 5,000 to 10,000 micro-seconds
seconds. To access data.

The price of a solid state drive is HDD is much cheaper than SSD
much more than an HDD

The SSD drive has no moving parts. The HDD has moving parts and
It uses flash memory to store data magnetic platters are used to store data

The SSD uses less power than a With all the parts and requirements to
standard HDD spin the platters the HDD uses more
power than an SSD

With no moving parts SSD generates HDD can sometimes be one of the
no noise loudest components in your computer
32
 CD-ROM
• Short for Compact Disc-Read Only Memory,

• A CD-ROM is an optical disc which contains audio or

software data whose memory is read only.

• A CD-ROM Drive or optical drive is the device used to

read them.

• CD-ROM drives have speeds ranging from 1x all the way

up to 72x, meaning it reads the CD roughly 72 times faster
than the 1x version.
33
Top CD-ROM Drive Problems and solutions

• Problem: Cannot read information on a CD or DVD.

Check all the cables, monitor, keyboard and mouse functionality.
Remove the disk and try to clean it with a commercial cleaning
fluid or a clean damp cloth.
Try to clean the disk drive with a disk cleaning CD or DVD.

34
Top CD-ROM Drive Problems and solutions
• Problem: Disc drive not working in Windows
Make sure you have tested more than one CD in the disc drive it
may be one CD that is bad or dirty.
Check Device Manager: Within Device Manager verify that the
CDROM has no exclamation marks or red Xs
Corruption in Windows: Try testing the CDROM in Safe Mode.

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End of chapter six