STORAGE DEVICES INTRODUCTION

STORAGE DEVICES

INTRODUCTION

There are many kinds of drives, but when someone talks about a drive, they usually mean a hard disk drive. Most computers these days also come with a CD-ROM drive (that can be a player only or a

player/recorder) or a DVD -ROM drive (again, either just a player or both a player and recorder). Many

computers also have a floppy disk drive. There are also removable drives, MO (magneto optical) drives,and tape drives. .

All the above disks that these drives handle are nonvolatile storage. In other words whatever you

store on the disk remains there, even after you shut off the PC. Disk drives are encased in metal boxes to keep them from being damaged. Hard disks are fixed disks whereas you can remove one disk and insert another in floppy drives and CD drives. Hard drives and CD drives uses three types of interfaces IDE, SATA and SCSI. All the above drives need a data connector and a power connector.

A disk drive rotates the disk very fast and has one or more heads that read and write data. There are different types of disk drives for different types of disks. For example, a hard disk drive (HDD) reads and writes hard disks, and a floppy drive (FDD) accesses floppy disks. A magnetic disk drive reads magnetic disks, and an optical drive reads optical disks.

Disk drives can be either internal (housed within the computer) or external (housed in a separate

box that connects to the computer).

HARD DISK

A hard disk drive (HDD), commonly referred to as a hard drive, hard disk or fixed disk drive, is a

non-volatile storage device which stores digitally encoded data on rapidly rotating platters with

magnetic surfaces. Strictly speaking, "drive" refers to a device distinct from its medium, such as a tape

drive and its tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, an HDD today is typically a sealed unit (except for a filtered vent hole to equalize air pressure) with fixed media.

HDDs record data by magnetizing ferromagnetic

material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material. A typical HDD design consists of a spindle which holds one or more flat circular disks called platters, onto which the data is recorded. The platters are made from a non-magnetic material, usually aluminum alloy or glass, and are coated with a thin layer of magnetic material.

The platters are spun at very high speeds. Information is written to a platter as it rotates past devices called read-and-write heads that operate very close (tens of nanometers in new drives) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. There is one head for each magnetic platter surface on the spindle, mounted on a common arm. An actuator arm (or access arm) moves the heads on an arc across the platters as they spin, allowing each head to access almost the entire surface of the platter as it spins.

A typical desktop HDD, might store between 120 and 300 GB of data, rotate at 7,200 revolutions

per minute (RPM) and have a media transfer rate of 1 Gbit/s or higher. Hard disk drives are accessed over one of a number of bus types, including parallel ATA (PATA, also called IDE or EIDE), Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS).following is the main difference between various connectors

o IDE/ATA

40-conductor connection (ATA)

80-conductor connection (UDMA)

Max cable length 80” (0.46 mtrs)

Max data transfer rate – 133Mbps

Data transfer methods – PIO, DMA & ATAPI

Max devices supported – 2

o SATA

Serial connection

Max data transfer rate – 3 to 150 Mbps

Modular type connection

o SCSI

50-conductor connection

Max devices supported – up to 16

Max data transfer rates – 5 to 160 Mbps

Max cable length – 12 mtrs

8/16 bits data bus width Bus s

CD-ROM

CD-ROM (an abbreviation of "Compact Disc read-only memory") is a Compact Disc that contains data accessible by a computer. While the Compact Disc format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data. CD-ROMs are popularly used to distribute computer software, including games and multimedia applications, though any data can be stored (up to the capacity limit of a disc). Some CDs hold both computer data and audio with the latter capable of being played on a CD player, whilst data (such as software or digital video) is only usable on a computer (such as PC CD-ROMs). A CD has a single spiral track of data, circling from the inside of the disc to the outside. A CD can store the data ranging from 650 to 900 MB.

Discs are made from a 1.2 mm thick disc of polycarbonate plastic, with a thin layer of aluminum to

make a reflective surface. The most common size of CD-ROM disc is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as numerous non-standard sizes and shapes (e.g. business card-sized media) are also available.

Data is stored on the disc as a series of microscopic indentations ("pits", with the gaps between them referred to as "lands"). A laser is shone onto the reflective surface of the disc to read the pattern of pits and lands. Because the depth of the pits is approximately one-quarter to one-sixth of the wavelength of the laser light used to read the disc, the reflected beam's phase is shifted in relation to the incoming beam, causing destructive interference and reducing the reflected beam's intensity. This pattern of changing intensity of the reflected beam is converted into binary data.

DVD

Digital Versatile Disk has same size as a CD but stores seven times CD capacity on a single side. DVDs can also be double-sided or dual layer. Today most DVDs are used to display full-length commercial motion pictures, plus additional material such as outtakes, director's notes, movie trailers, etc.

DVD, introduced in 1996, was originally known as Digital Video Disc but soon became known as

Digital Versatile Disc. It is the next generation of optical disc storage technology, which shares the same overall dimensions of a CD, but have significantly higher capacities - holding from 4 to 28 times as much data. Single sided DVDs can store 4.7GB for single layer and 8.5GB for dual-layer disks. Double-sided DVDs can store 9.4GB for single layer and 17GB for dual-layer disks.

BLU-RAY DISC

Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium. Its main uses are

high-definition video and data storage. The disc has the same physical dimensions as standard DVDs and CDs.

The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write this

type of disc. Because of the beam's shorter wavelength (405 nano meters), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A two-layer Blu-ray Disc can store 50 gigabytes, almost six times the capacity of a two-layer DVD, or ten times that of a single-layer DVD.

During the format war over high-definition optical discs, Blu-ray Disc competed with the HD DVD

format. On February 19, 2008, Toshiba—the main company supporting HD DVD—announced that it would no longer develop, manufacture, and market HD DVD players and recorders, leading almost all

other HD DVD companies to follow suit, effectively ending the format war.

Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of October 29, 2008, more than 1010 Blu-ray Disc titles have been released in the United States and more than 550 Blu-ray Disc titles have been released in Japan. There are expected to be over 1300 Blu-ray Disc titles released in the United States by the end of 2008.

FLASH MEMORY

Flash memory is an evolving technology. The first generation of chips required that your PC or other device using the chips handle all the minute of the erase and write operations. Current generation chips have their own onboard logic to automate these operations, making Flash ROM act more like ordinary memory. The logic controls the timing of all the pulses used to erase and write to the chip, ensures that the proper voltages reach the memory cells, and even verifies that each write operation was carried out successfully. Fig. shows a type of Flash memory card.

On the other hand, we can say that Flash memory is a type of semiconductor memory which uses its own logic gates to store the data.the name flash was derived from the comparision with a camera flash like action for writing and erasing of data. For the most effective operation and longest life, however, these require special operating systems (or modified versions of familiar operating systems) that minimize the number of erase and reprogramming cycles.

For system designers, the electrical re-programmability of Flash ROM makes it easy to use. Unfortunately, Flash ROM is handicapped by the same limitation as EEPROM—its life is finite (although longer than ordinary EEPROM) and it must be erased and reprogrammed as one or more blocks instead of individual bytes.A USB flash drive consists of a NAND-type flash memory data storage device integrated with a USB (universal serial bus) interface. USB flash drives are typically removable and rewritable, much shorter than a floppy disk (1 to 4 inches or 2.5 to 10 cm), and weigh less than 2 ounces (56 g). Storage capacities typically range from 64 MB to 64 GB with steady improvements in size and price per gigabyte. Some allow 1 million write or erase cycles and have 10-year data retention, connected by USB 1.1 or USB 2.0.

USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk. They have a more compact shape, operate faster, hold much more data, have a more durable design, and operate more reliably due to their lack of moving parts. Additionally, it has become increasingly common for computers to ship without floppy disk drives. USB ports, on the other hand, appear on almost every current mainstream PC and laptop. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Mac OS X, Linux, and other Unix-like systems. USB drives with USB 2.0 support can also operate faster than an optical disc drive, while storing a larger amount of data in a much smaller space.

Nothing actually moves in a flash drive: the term drive persists because computers read and write flash-drive data using the same system commands as for a mechanical disk drive, with the storage appearing to the computer operating system and user interface as just another drive.

A flash drive consists of a small printed circuit board protected inside a plastic, metal, or rubberized case, robust enough for carrying with no additional protection — in a pocket or on a key chain, for example. The USB connector is protected by a removable cap or by retracting into the body of the drive, although it is not liable to be damaged if exposed. Most flash drives use a standard type-A USB

connection allowing plugging into a port on a personal computer.

HARD DISK DRIVE

A hard disk drive (HDD), commonly referred to as a hard drive, hard disk, or fixed disk drive, is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. Formatting

Disk formatting is the process of preparing a hard disk or other storage medium for use, including

setting up an empty file system. A variety of utilities and programs exist for this task.

Large disks can be partitioned, divided into logical sections that are formatted with their own file systems. This is normally only done on hard disks because of the small sizes of other disk types, as well as compatibility issues.

A corrupted operating system can be reverted to a clean state by formatting the disk and reinstalling the OS, as a drastic way of combating a software problem or malware infection. Obviously,important files should be backed up beforehand.

High-level formatting

High-level formatting is the process of setting up an empty file system on the disk, and installing a boot sector. This alone takes little time, and is sometimes referred to as a "quick format". In addition, the entire disk may optionally be scanned for defects, which takes considerably longer, up to several hours on larger hard disks.

Installing hard drive

Drive preparation:

You will have to setup and prepare your drives before installing them into the case and attaching

the appropriate cables to them. There are jumpers on the back of all IDE devices determining their status in the drive chain.

The jumpers have three or more positions that they can be set at by the movement of a plastic

tab that select the device as a Master, Slave or Cable select drive. See fig- showing jumper-setting options on hard driver.

In most hard drive that is a brand new the default setting is a Master or Cable select device so you

shouldn't have to adjust the jumpers as this will enable the device to get detected automatically by the

system.

Top performance of a Hard Drive is not so critical. Some cases requires the bracket that attach to

the sides of the drive before placing them in the case (see fig 6.8) but most just get secured by just using a couple of screws. Just slide the drive into the case and with the bracket system the drive will lock into place.

Hard disk Partitioning

How to partition and format the hard disk using the Windows XP Setup program You can use the Windows XP Setup program to partition and format the hard disk. To do this, use the following steps:

Step 1: Partition the hard disk

a. Insert the Windows XP CD into your CD or DVD drive, or insert the first Windows XP Setup disk into the floppy disk drive, and then restart the computer to start the Windows XP Setup program.

Note: If you are using the Windows XP Setup disks, insert each additional disk when you are prompted, and then press ENTER to continue after you insert each disk.

b. If you are prompted, select any options that are required to start the computer from the CD or DVD drive.

c. If your hard disk controller requires a third-party original equipment manufacturer (OEM) driver, press F6 to specify the driver.

d. At the Welcome to Setup page, press ENTER.

e. Press F8 to accept the Windows XP Licensing Agreement.

f. If an existing Windows XP installation is detected, you are prompted to repair it. To bypass the repair, press ESC.

g. All existing partitions and non-partitioned spaces are listed for each physical hard disk. Use the ARROW keys to select an existing partition, or create a new partition by selecting the non-partitioned space where you want to create a new partition. You can also press C to create a new partition using non-partitioned space.

h. Note If you want to create a partition where one or more partitions already exist, you must first delete the existing partition or partitions, and then create the new partition. You can press D to delete an existing partition, and then press L (or press ENTER, and then press L if it is the System partition) to confirm that you want to delete the partition. Repeat this step for each existing partition that you want to include in the new partition. When all the partitions are deleted, select the remaining non-partitioned space, and then press C to create the new partition.

i. To create the partition with the maximum size, press ENTER. To specify the partition size, type the

size in megabytes (MB) for the new partition, and then press ENTER.

j. If you want to create additional partitions, repeat steps g. and h.

k. To format the partition and install Windows XP, follow the screen instructions for formatting. If you do not want to install Windows XP, press F3 two times to exit the Windows Setup program. Note –the method mentioned here is basic method of partition. If we have to partition without installing OS there are various third party software like “Partition Magic” is available with the help of which partition can be done easily.

CD ROM DRIVE

CD-ROM discs are read using CD-ROM drives, which are now almost universal on personal computers. A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, S-ATA, Fire wire, or USB interface or a proprietary interface, such as the Panasonic CD interface. Virtually all modern CD-ROM drives can also play audio CDs as well as Video CDs and other data standards when used in conjunction with the right software.CD-ROM drives employ a near-infrared 780 nm laser diode. The laser beam is directed onto the disc via an opto-electronic tracking module, which then detects whether the beam has been reflected or scattered.

The rate at which CD-ROM drives can transfer data from the disc is gauged by a speed factor relative to music CDs: 1x or 1-speed which gives a data transfer rate of 150 kilobytes per second in the most common data format. By increasing the speed at which the disc is spun, data can be transferred at greater rates. For example, a CD-ROM drive that can read at 8x speed spins the disc at up to 4000 rpm (compared to the 500 rpm maximum for 1x speed), giving a transfer rate of 1.2 megabytes per second. The fastest transfer rate commonly available is about 52x or 10,350 rpm and 7.62 megabytes per second, though this is only when reading information from the outer parts of a disc.

The CD player has the job of finding and reading the data stored as bumps on the CD. Considering

how small the bumps are, the CD player is an exceptionally precise piece of equipment. The drive consists of three fundamental components:

• A drive motor spins the disc. This drive motor is precisely controlled to rotate between 200 and 500 rpm depending on which track is being read.

• A laser and a lens system focus in on and read the bumps.

• A tracking mechanism moves the laser assembly so that the laser's beam can follow the spiral track. The tracking system has to be able to move the laser at micron resolutions.

DIGITAL VERSATILE DISC

DVD (also known as "Digital Versatile Disc" or "Digital Video Disc") is a popular optical disc storage media format. Its main uses are video and data storage. Most DVDs are of the same dimensions as compact discs (CDs) but store more than six times as much data.

Variations of the term DVD often describe the way data is stored on the discs: DVD-ROM has data

which can only be read and not written, DVD-R and DVD+R can only record data once and then function as a DVD-ROM. DVD-RW, DVD+RW and DVD-RAM can both record and erase data multiple times. The wavelength used by standard DVD lasers is 650 nm, and thus has a red color.

DVD-Video and DVD-Audio discs respectively refer to properly formatted and structured video and audio content. Other types of DVDs, including those with video content, may be referred to as DVD-Data discs. As next generation High definition optical formats also use a disc identical in some aspects yet more advanced than a DVD, such as Blu-ray Disc. The basic types of DVD are referred to by a rough approximation of their capacity in gigabytes.

The 12 cm type is a standard DVD, and the 8 cm variety is known as a mini-DVD. These are the

same sizes as a standard CD and a mini-CD, respectively. Each DVD sector contains 2418 bytes of data, 2048 bytes of which are user data.

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