Assignment Chapter 7 From Mr Tri Djoko Wahjono, Ir,M.Sc

ASSINGNMENT CHAPTER 7

Chapter Review Pages 384 – 385

Discovering Computer (“Living In the Digital World 2011”)

Lecture     :      Mr. Tri Djoko Wahjono,Ir, M.SC

Student     :      Williem [1701309721]

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

A.  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.

B.  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.

C.  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.

D.  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.