Computer Storage

Digital versatile discs

DVDs Used in optical drives Store between 4 and 8.5 gigabytes of data Most DVD drives are capable of reading CDs and DVDs

Traditional hard drive

Desktop computer's primary storage device Also called "hard disk" Uses spinning, magnetized platters to store data Also the primary storage device in servers and many laptops

Byte

Unit of digital information that commonly consists of 8 bits Represented by "B" Historically, the space needed to store a character of information, such as one letter or one number "Bite" was intentionally misspelled as "byte" so it wouldn't be mistaken for "bit"

Gigabyte

Unit of digital storage consisting of approximately one billion bytes Represented by "GB" Standard unit of measurement for memory and storage in computers Enough capacity to store 250 MP4 music files

Megabyte

Unit of storage consisting of approximately one million bytes Represented by "MB" Enough data to fill four books worth of text

Helium hard drives

Use helium instead of air inside the hard drive Helium is less dense. This allows more platters within the same space Platters stay cooler and can spin faster 20-30% more efficient than air-filled hard drives

How a Blu-ray works

Uses a shorter wavelength "blue" laser so that it can store more data Disc stores information with a reflective coating on a plastic disc The reflective coating has pits, which absorb laser beam light, and lands, which reflect laser beam light The Blu-ray player detects and reads the reflected laser light

Holographic data storage

Uses a split laser beam to write data onto photo-receptive substrates Because the beam can strike receptors from different angles, many bits of data can be stored in the same physical location Theoretically, holographic storage should be capable of storing gigabytes of data in a single cubic millimeter

Memristor storage

Uses an advanced circuit element called a memristor Memristors have variable resistance based on the history of current that has passed through the element A single memristor could replace many transistors This means the chip could be far smaller and far faster

How CDs work

A compact disc stores data on a plastic disc with a reflective coating This coating has pits, which absorb laser beam light, and lands, which reflect laser beam light The laser beam's reflection is detected by the CD player Pits and lands, shown under an electron microscope, store data on a CD

How DVDs work

A digital versatile disc stores information with a reflective coating on a plastic disc The reflective coating has pits, which absorb laser beam light, and lands, which reflect laser beam light The DVD player detects and reads the reflected laser light

Optical drives

A storage device that writes and reads data with a laser Works by rotating a disc with a reflective coating Coating is read by a laser beam within the optical drive's read/write head Speed of an optical drive is measured in revolutions per minute (RPM) Disc itself (DVD, Blu-ray, CD) is referred to as the optical media

Solid state drives (SSD)

All-electronic storage devices Used in a variety of products, smartphones, cameras, and tablet computers No physical moving parts - makes them faster, more energy efficient, and more durable than traditional magnetic hard drives

Storage

Allows computers to retain data when the device is turned off Keeps programs, photos, videos, and other data files for future use Sometimes referred to as "secondary storage"

Audio file compression

Allows extremely small devices to store large numbers of music files MP4 --Most popular lossy compression format WAV --Most popular lossless compression format

Video file compression

Allows you to store many movies on tablets and other digital devices MPEG-2: --Most popular video compression format --Lossy --Used on commercial DVDs MPEG-4: --Lossy --Used by individuals --Can compress video files by factors of 20 to 200

Storage capacity

Amount of space you have available to save data Usually measured in gigabytes (billions of bytes) and terabytes (trillions of bytes) OSs & large apps (such as MS Office) use significant amounts of storage. Typical laptop - 500GB to 1TB Typical smartphone -16 to 128GB

Terabyte

Approximately 1 trillion (1,000,000,000) bytes Represented by "TB" Approximately enough data to store 230 DVD movies

Petabyte

Approximately 1,000 trillion bytes Represented "PB" Standard unit of measurement of server banks

Bit

Binary digit - smallest unit of digital data storage Represented by a "b" Can only have one of two possible values Examples --Magnets either attract or repel another magnets --Transistor, an electronic switch, either lets electrons pass, or stops electrons

Compact discs

CDs Used in optical drives Can store approximately 700 megabytes of data CDs are most commonly used to store audio files. Over 300,000,000 music CDs have been sold world-wide!

Kilobyte

Equals approximately 1,000 bytes Represented by "KB" A page of text uses about 4KB

DNA Storage

If kept in dry, dark areas, DNA could store extremely large amounts of data for thousands of years While theoretically feasible, technical obstacles such as reducing writing and access times make DNA storage a distant data storage solution

Storage challenges

Increased storage will be needed 300 hours of YouTube videos are uploaded every minute Biologists estimate that mapping the genomes of individual patients will require even more storage space within the next ten years

How SSDs work

Integrated circuits to store data The same flash technology that is used in making USB drives (thumb drives) Unlike ordinary transistors, flash technology uses special transistors that not only work as switches, but also remain in the correct position when power is turned off

USB drives

Often called thumb drives or flash drives Solid state, are all-electronic storage devices Can be used with nearly any computer, including laptops, desktops, all-in-ones, and tablets Many televisions also accept USB drives. Smartphones and cameras often use USB drives with adapters

Blu-ray discs

Optical media used in optical drives Store up to 50 GB of data Most Blu-ray drives are capable of reading CDs, DVDs, and Blu-ray discs

Storage devices

Provide for additional data retention Allow data to be backed up (copied) Examples include: --External hard drives --Optical drives --Solid state drives --USB drives (flash or thumb drives)

Redundant Array of Independent Discs

RAID Uses multiple layers of hard disc drives to provide back-ups for all stored data Server banks often use RAIDs to store data In a RAID, if one hard disc drive crashes, the data is easily recovered from another hard disc drive

File compression

Reduces the size of data files Saves storage space Saves transmission capacity and can speed data transmission 2 types of file compression: --Lossy compression removes less valuable data --Lossless compression eliminates redundancy and retains all the original data

Image file compression

Reduces the size of photo files Popular image compression formats include: --JPEG - most popular lossy format --PNG - most popular lossless format --GIF - largely replaced by PNG

Storage capacity

Refers to the size of the computer's hard drive Typical laptop - 500 GB to 1TB Typical tablet -16 GB to 256 GB A standard definition movie uses 1 to 2 GB of storage, while an HD movie uses 3 to 5 GB

Cloud storage

Saving your files to servers on the Internet There are many ways of using cloud storage Most common - simply attach files to Email and then send it to yourself. Open an account with Picasa, Flickr, Windows Live Photo Gallery, or any other of the numerous photo service websites. Purchase secure server space from an online supplier.

How cloud storage works

Servers act like giant hard drives Users simply upload, or send, their files to the server for storage The files are backed-up onto multiple servers If one server crashes, data is not lost Users can download their files onto any Internet-connected device

How traditional hard drives store data

Store data on spinning metal discs with a magnetized coating A magnetically tipped actuator arm, called a read/write head, "senses" the magnetic coating on the disc A read/write head looks similar to a needle on a record player. Unlike a needle, a read/write head never touches the disc The read/write head either transmits data to the computer's processor, or changes/rewrites the data Because the disc mechanically spins, hard disc drives have longer access times than solid state hard drives

Storage media

The specific item that retains the data While a DVD drive is a storage device, the DVDs themselves are the storage media Blu-ray discs are also storage media Some consider USB drives, thumb, or flash drives storage media. Others categorize them as storage devices

Access time

Time it takes data to reach your computer's processor With a traditional magnetic hard drive, access time is considered the time it takes for the read/write head to locate the correct sector on the disc Solid-state drives and flash drives provide data in significantly shorter access time than traditional magnetic hard drives