Lecturer: Mr. Tri Djoko Wahjono, Ir, M.Sc.
By: Veronica Ong (1701317660) of class 01PCT
Task: Chapter Review of Chapter 7 from the Textbook Discovering Computers.
1. How
Are Storage Devices Different from Storage Media?
Storage device refers to the apparatus for
recording computer data. Examples are the RAM, floppy drives, ZIP drives, and
other disks drives. While, storage media are the materials on which data are
written and stored or a devices that store application and user information.
Examples are the floppy disks, optical discs, hard disks, etc.A storage device is the computer hardware
that records and/or retrieves items to and from storage media.
2. What Are the Characteristics of an Internal Hard Disk?
A hard
disk drive (HDD)
is a data
storage device used
for storing and retrieving digital information
using rapidly rotating disks (platters) coated with magnetic material. An HDD retains
its data even
when powered off. Data is read in a random-access manner,
meaning individual blocks of
data can be stored or retrieved in any order rather than sequentially.
An HDD consists of one or more rigid ("hard") rapidly rotating disks
(platters) with magnetic heads arranged on a moving actuator arm
to read and write data to the surfaces.
The primary characteristics
of an HDD are its capacity and performance
·
The capacity of a hard disk
Is determined
from whether it uses longitudinal or perpendicular recording, the number of
platters it contains, and the composition of the magnetic coating on the
platters.
·
Performance
Time
to access data
The factors that limit the time to access the
data on an HDD are mostly related to the mechanical nature of
the rotating disks and moving heads. Seek
time is a measure of how long it takes the head assembly to
travel to the track of the disk that contains data. Rotational latency is incurred because the desired disk sector may not be
directly under the head when data transfer is requested. These two delays are
on the order of milliseconds each. The bit
rate or data transfer rate (once the head is in the right
position) creates delay which is a function of the number of blocks
transferred; typically relatively small, but can be quite long with the
transfer of large contiguous files. Delay may also occur if the drive disks are
stopped to save energy.
Time to access data can be
improved by increasing rotational speed (thus reducing latency) and/or by
reducing the time spent seeking. Increasing areal density increases throughput by increasing data rate and by increasing the amount of
data under a set of heads, thereby potentially reducing seek activity for a
given amount of data.
Seek
time
Seek time has continued to improve slowly over time. Some desktop
and laptop computer systems allow the user to make a tradeoff between seek performance
and drive noise. Faster seek rates typically require more energy usage to
quickly move the heads across the platter, causing louder noises from the pivot
bearing and greater device vibrations as the heads are rapidly accelerated
during the start of the seek motion and decelerated at the end of the seek
motion. Quiet operation reduces movement speed and acceleration rates, but at a
cost of reduced seek performance.
Latency
Latency is the delay for the rotation of the disk
to bring the required disk sector under the
read-write mechanism. It depends on rotational speed of a disk, measured in revolutions per minute (rpm). Average rotational latency is shown in the table
below, based on the statistical relation that the average latency in
milliseconds for such a drive is one-half the rotational period.
Data Transfer rate
HDD data transfer rate depends upon the
rotational speed of the platters and the data recording density. Because heat
and vibration limit rotational speed, advancing density becomes the main method
to improve sequential transfer rates. Higher speeds require more power absorbed
by the electric engine, which hence warms up more. While areal density advances
by increasing both the number of tracks across the disk and the number of
sectors per track, only the latter increases the data transfer rate for a given
rpm. Since data transfer rate performance only tracks one of the two components
of areal density, its performance improves at a lower rate.
3. What
Is the Purpose of Network Attached Storage Devices, External and Removable Hard
Disks, and Hard Disk Controllers?
·
Network
Attached Storage Device
NAS
is useful for more than just general centralized storage provided to client
computers in environments with large amounts of data. NAS can enable simpler
and lower cost systems such as load-balancing and fault-tolerant email and web
server systems by providing storage services.
File-level
computer data storage connected
to a computer network providing data access to a heterogeneous group of clients. NAS
not only operates as a file
server, but is specialized for this task either by its hardware, software, or
configuration of those elements.
·
External
and Removable Hard Disks
An
external hard disk is a separate freestanding hard disk that connects with a
cable to a USB or FireWire port on the system unit or communicates wirelessly.
External hard disks have storage capacities up to 4 TB and more.
A
removable hard disk can be inserted or removed from a built-in or external
drive. Removable hard disks have storage capacities up to 1 TB
·
Hard
Disk Controller
Controller
consists of a special-purpose chip and electronic circuits that control the
transfer of data, instructions, and information from a disk to and from the
system bus and other components in a computer. A hard disk controller may be
part of the hard disk on the motherboard, or it may be a separate
4. What
Are the Various Types of Flash Memory Storage?
·
A solid state drive (SSD)
Typically
uses flash memory to store data, instructions, and information. Data storage device using integrated circuit assemblies as memory to store data persistently. SSD technology uses electronic interfaces compatible with
traditional block input/output (I/O) hard
disk drives, thus permitting simple replacement in
common applications.
·
A memory card
Is a
removable flash memory device that you insert and remove from a slot in a
computer, mobile device, or card reader or writer. Common memory cards include
CompactFlash, Secure Digital (SD), Secure Digital High Capacity (SDHC), micro
SD, microSDHC, xD Picture Card, Memory Stick, and Memory Stick Micro (M2).
·
A USB flash drive
Sometimes
called a thumb drive, is a flash memory storage device that plugs in a port on
a computer or mobile device.
·
An Express Card module
Is
a removable device that it’s in an Express Card slots. Express Card modules can
add memory, storage, communications, or other capabilities to a computer.
5. What
Is Cloud Storage, and What Are Its Advantages?
Cloud storage is a model of networked enterprise storage where data is stored in virtualized pools of storage which
are generally hosted by third parties. Hosting companies operate large data centers, and people who
require their data to be hosted buy or lease storage capacity from them or
Internet service that provides storage for computer users.
Advantage
of Cloud storages:
·
Companies need only pay for the storage they
actually use, typically an average of consumption during a month. This
does not mean that cloud storage is less expensive, only that it incurs operating
expenses rather than capital expenses.
·
Organizations can choose between off-premise
and on-premise cloud storage options, or a mixture of the two options,
depending on relevant decision criteria that is complementary to initial direct
cost savings potential; for instance, continuity of operations (COOP), disaster
recovery (DR), security (PII, HIPPA, SARBOX, IA/CND), and records retention
laws, regulations, and policies.
·
Storage availability and data protection is
intrinsic to object storage architecture, so depending on the application, the
additional technology, need effort and cost to add availability and protection
can be eliminated.
·
Storage maintenance tasks, such as purchasing
additional storage capacity, are offloaded to the responsibility of a service
provider.
·
Cloud storage provides users with immediate
access to a broad range of resources and applications hosted in the
infrastructure of another organization via a web service interface.
·
Cloud storage can be used for copying virtual
machine images from the cloud to on-premise locations or to import a virtual
machine image from an on-premise location to the cloud image library. In
addition, cloud storage can be used to move virtual machine images between user
accounts or between data centers.
·
Many Cloud Storage providers offer free
accounts which can be expanded through various techniques, which many people
have started to take advantage of to get hundreds of gigabytes of free online
storage.
6. What
Are the Characteristics of Optical Discs?
Is a flat, usually circular disc which encodes binary data
(bits) in the form of pits
(binary value of 0 or off, due to lack of reflection when read) and lands
(binary value of 1 or on, due to a reflection when read) on a special material
(often aluminum) on one of its flat surfaces. The encoding material sits atop a
thicker substrate (usually polycarbonate) which makes up the bulk
of the disc and forms a dust defocusing layer. The encoding pattern follows a
continuous, spiral path covering the entire disc surface and extending from the
innermost track to the outermost track. The data is stored on the disc with a laser or
stamping machine, and can be accessed when the data path is illuminated with a laser
diode in
an optical
disc drive which
spins the disc at speeds of about 200 to 4,000 RPM or
more, depending on the drive type, disc format, and the distance of the read
head from the center of the disc (inner tracks are read at a higher disc
speed). The pits or bumps distort the reflected laser light, hence most optical
discs (except the black discs of the original PlayStation video game console)
characteristically have an iridescent appearance
created by the grooves of the reflective layer. The reverse side of an optical
disc usually has a printed label, sometimes made of paper but often printed or
stamped onto the disc itself. This side of the disc contains the actual data
and is typically coated with a transparent material, usually lacquer.
Unlike the 3½-inch floppy
disk, most optical discs do not have an integrated protective casing and are
therefore susceptible to data transfer problems due to scratches, fingerprints,
and other environmental problems. Optical discs, which primarily store
software, data, digital photos, movies, and music, contain microscopic pits
(indentations) and lands (flat areas) in their middle layer. Optical discs
commonly store items in a single track that spirals from the center of the disc
to its edge. Like a hard disk, the ingle track is divided into evenly sized
sectors.
7. How Are the Various
Types of Optical Discs Different?
There are numerous formats of optical direct
to disk recording devices
on the market, all of which are based on using a laser to change the reflectivity of
the digital
recording medium
in order to duplicate the effects of the pits and lands created when a
commercial optical disc is pressed. A CD-ROM, or compact disc read-only
memory, is a type of optical disc that uses laser technology to store items
Users can read the contents of standard CD-ROMs but cannot erase or modify
their contents. Formats such as CD-R and DVD-R are
"Write once read many" is a multisession disc on which users
can record their own items, such as text, graphics, and audio, while CD-RW and DVD-RW are
rewritable, more like a magnetic recording hard
disk drive (HDD).
8. How Are Tape, Magnetic Stripe Cards, Smart Cards, Microfilm
and Microfiche, and Enterprise Storage Used?
·
Tape
§
A tape drive is a data storage device that reads and writes data on a magnetic
tape. Magnetic
tape data storage is typically used for offline, archival data storage. Tape
media generally has a favorable unit cost and long archival stability.
·
A Magnetic
Stripe Card
§
Is a type of
card capable of storing data by modifying
the magnetism of tiny iron-based magnetic particles on a band of magnetic
material on the card. The magnetic stripe, sometimes called swipe card or magstripe,
is read by swiping past a magnetic
reading head. Such as credit
card, entertainment card, bank card, or other similar card with a stripe that
contains information identifying you and the card. A magnetic stripe card
reader reads the information stored on the stripe.
·
A
Smart Card
·
Any pocket-sized card with embedded integrated
circuits.
·
Smart cards are made of plastic, generally polyvinyl
chloride, but sometimes polyethylene terephthalate based polyesters, acrylonitrile
butadiene styrene or polycarbonate.
Since April 2009, a Japanese company has manufactured reusable financial smart
cards made from paper. Smart cards can provide identification, authentication,
data storage and application processing. Smart cards may provide strong security
authentication for single
sign-on (SSO)
within large organizations.
·
Microfilm
and microfiche
·
Microfilm is essentially 35mm photographic
film that was used to take images of the pages of a book, a periodical volume
or a newspaper. The reel of film is then duplicated and sold to
libraries. Microfiche are flat sheets of photographic film about 4×6
inches in size. Reduce the amount of paper must handle, are inexpensive, and
have the longest life of any storage media. Enterprises use computers, servers,
and networks to manage and store huge volumes of data and information.
·
Enterprise
Storage
·
Is the computer data
storage designed for large-scale, high-technology environments of
the modern enterprises. When comparing to the consumer storage, it has higher scalability, higher reliability, better fault
tolerance, and much higher initial price.
Some storage systems can provide more than 185 TB of storage, and optical disc
servers hold hundreds of optical discs.
·
From the salesperson's
point of view, the four main enterprise storage markets are:
·
Online storage - large disk
array solutions, minimizing access time to the data, and
maximizing reliability;
·
Backup - off-line storage for data
protection, with a smaller price per byte than online storage, but at a cost of
higher average access time; often uses sequential access storage,
such as tape libraries;
·
Archiving - technically similar
to backup, but its purpose is long-term retention, management, and
discovery of fixed-content data to meet regulatory compliance, litigation
protection, and storage cost optimization objectives;
·
Disaster recovery solutions, used to protect the data from localized disasters,
usually being a vital part of broader business continuity plan.
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