Data Storage and Storage Devices

Welcome to guide on Data Storage and the various data storage devices.  Hope this would be helpful to you!

  1. What is data storage?
    • Data storage is where we put data in a known place (save). And later get that data back again (read)
      • Writing /Saving data = storing Data
      • Getting our data back again from the storage location = Reading/Opening Data
  2. Difference between Backing Storage and RAM
    • RAM
      • Used to store data temporarily
      • It is volatile in nature, which means when PC is switched off, the data is erased
      • Used to store data that is currently in use e.g. open programs, etc
      • Very fast reading/writing of data
    • Backing Storage
      • Slow reading/writing
      • Non volatile, does not lose data when PC is off
      • Can hold information for very long time
  3. What is backing up?
    • Backing up is the process of using a storage device to copy files and also data to a different storage medium.  In case of a problem with original copy, backing up data is considered good practice in computing and protects us from accidental or deliberate loss of our work or files
    • Backups are often stored in a different place to the original copy.  This is to protect against irretrievable loss such as damage by fires, floods or theft.
  4. Why back up data?
    • There are many reasons why backups are made.  Some common ones are given below
      • Data could be lost due to damage to the original storage device. e.g. the hard disk in your PC could stop spinning
      • Original data could be accidentally written or copied over
      • Hackers could illegally access data and alter or delete it
  5. What is a Storage Device?
    • The hardware that saves (writes)/reads the storage medium (DVD Player)
  6. What is a Storage Medium?
    • The hardware that actually holds the data e.g., Hard Disk Drive (HDD), Pen drives, DVD, etc
  7. What are the different ways in which data is stored and read or What are the different types of access?
    • Direct Access:
      • This method is used with storage devices – In-storage devices such as magnetic media (HDDs) and Optical medium (CDs, DVDs, etc)
      • The computer can directly search where the data is stored and go to it directly
      • This is much faster than serial access
      • When stored information needs updating, the direct access device, will write data to the next available space and is position is recalculated by the computer
      • An example of direct access is a DVD movie where unlike a film reel tape, you can jump to any scene on the DVD.
    • Serial/Sequential Access:
      • Accesses data while starting at the beginning and works through bit by bit until the required information is found (kind of like an old film reel where the movie starts at the beginning and the data is read in order until the movie is finished).
      • Used on very slow magnetic tape systems where data recovery is slow.
      • When information on magnetic tape needs updating, an additional tape is required so that the old data can be merged with the new data.
      • Serial access is used in applications where speed is not important e.g., in utility billing, clearing bank cheques and making payslips.
  8. What are the types of storage?
    • There are three types of storage and each type stores data in a different way:
      • Magnetic Storage Media (HDDs and tapes)
      • Optical Storage Media (CD-ROMs and Blue Ray)
      • Solid State Devices (SSDs) storage
  9. Write examples of storage devices:
    • Fixed Hard Disk Drives
    • Magnetic tapes
    • Flash Memory
    • Micro Flash Memory
    • Memory stick
    • Floppy Disk
    • DVD-RAM
    • External HDD
    • External HDD
    • CD-ROM
    • DVC ROM
    • Blu Ray
  10. Explain Fixed Hard Disk Drive (HDD):
    • Used in all PCs and are the main method of storing data
    • The disk surface (platter) is coated in a magnetic film which is where the data is stored
    • These have R/W heads, which allow the data to be written or read from the disk
    • HDDs are used to store Operating System (OS), software applications and all other files
    • Typical storage spaces are 250 GB to 1 TB
    • Uses of Fixed HDDs
      • Used to store OS and application software (Windows word, excel, etc)
      • Used for storing files and documents (e.g., home work, music)
      • Real time systems (Robots, chemical plant control system) and online systems (booking airline tickets, etc) use HDD to store data
      • Used in file servers on PC networks to store files
    • Advantages of HDDs
      • Fast R/W times (saves data to disk and reads back from it quickly)
      • Huge capacities (can store 1000s of movies and music files)
      • Very easy to update/delete files
    • Disadvantages of HDDs
      • Can be damaged easily when computer is not shut down properly (disk crash)
      • Not portable as they are designed to be fixed to the computer and not removed
  11. What are Portable HDDs?
    • Portable HDDs
      • Work in similar way to an internal HDD but are connected to a computer externally via an USB port
      • Portable HDDs are designed to be transportable
      • They come with an USB cable to allow for easy attachment which allows for easy backing up/sharing of data between two or more people
      • Because they are used outside of the PC they come with protective covering to avoid physical damage to the HDD
      • Typical storage spaces are 250 GB to 1 TB
    • Uses of Portable HDDs
      • Can be used as portable backup systems to avoid loss of data
      • Used to transfer data, files and software between PCs via USB connectivity
    • Advantages of Portable HDDs
      • Fast R/W times
      • Huge capacities
      • Small and light with protective casing makes them perfect for transporting data between computers easily
      • Designed to plug into almost any computer via USB ports
    • Disadvantages of Portable HDDs
      • Can be damaged when computer is not shut down properly
      • Protective casing will only protect against minor bumps.  If the device is dropped, it can still become damaged.  This is a risk when transporting data externally
      • More expensive than other forms of storage
  12. Explain Floppy Disck Drives:
    • Old method of external data storage where information is held on a thin plastic disk which rotates.  As the disk rotates, a read write head is used to add or read data.  The disk of plastic is protected by a retractable metal sleeve and hard plastic housing.  A small notch provides write protection.  Maximum storage on a floppy disk is about 144 MB.
    • Uses
      • Still used where very small files need to be transferred or stored (e.g smal word processor document)
      • Write protect facility is useful to prevent accidental over writing of data
    • Advantages
      • Costs very little to buy
      • Can be write protected easily which protects against accidentally copying over files
    • Disadvantages
      • Very low storage capacity when compared to other methods (1.44 MB)
      • Very few computers have floppy disk drives
      • Floppy disks are very delicate and easy to damage
      • Slow data transfer rate takes long time to save or read data from the disk
  13. Magnetic Tapes
    • Thin strip of magnetic coated plastic which is wrapped onto a reel.  Data is stored on the magnetic plastic in the form of zeros and ones (binary). Data is written to and read from in sequence i.e. in order which is also known as serial access.  This type of storage is not useful for real time applications because it is very slow
    • Uses
      • Used where extremely large amounts of data need to be backed up
      • Used where speed of reading/writing of data is not a priority
      • Used in batch processing applications such as clearing bank cheques and producing pay slips
      • Used for backup of file servers on computer networks in schools and businesses (e.g. your files are backed up on the school network)
    • Advantages
      • Generally less expensive than the equivalent capacity HDD
      • Very Robust
      • Very large storage capacities (upto 5 TB or 5 trillion characters)
    • Disadvantages
      • Very slow data access/transfer (reading data back from the tape is slow)
      • Needs another tape to update data (i.e. original tape with changes = updated tape)
  14. Optical Storage Devices
    1. CD ROM & DVD ROMs
      • CD ROMs and DVD ROMs are read only memory.  This means that the data can’t be written over (added to) and can only be read
      • Uses
        • CD ROMs are used by manufacturers to store smaller files (up to 800 MB)
        • Music CDs, Electronic books, etc
        • Softwares such as Microsof word, etc
        • DVD ROMs have larger storage capacities (upto 4.7 GB) than CD ROMs and are used to store larger files such as
          • Movies
          • Large games such as Call of Duty
      • Advantages
        • Holds more data than floppy disk
        • Less expensive than HDD
      • Disadvantages
        • Very slow data access/data transfer when compared to a hard disk (reading data back from the CD/DVD is slow)
    2. CD-R and DVD-R
      • The letter R means that the disk is recordable once only
      • Once the disk has been recorded on it, it becomes CD or DVD ROM
      • Data is burned onto the disk using a special drive (called disk burner)
      • Data can be added to the disk but not erased
      • Thin layer of metallic dye is used to record only
      • When the CD-R and DVD-R are burnt, the laser makes permanent marks (dots of data which represent 1 and 0) onto the metallic dye
      • Uses
        • Used to create home recording of music (CD-R’s) and movies (DVD-R’s)
        • They can be used to transfer data from one computer to another
        • Useful for situations where accidental deletion of data is out of question (e.g. Important personal records)
      • Advantages
        • Cheaper than the RW disc and hard disk drive
        • Physically impossible to accidentally delete important information stored on them
        • Easy way of transporting information from one computer to another.
        • Disadvantages
        • Only recordable once.  This means updating data is impossible
        • If error occurs during burning then the disk is damaged and must be thrown away (wasted)
        • Not all CD/DVD players can read CDR or DVD-R
    3. CD-RW and DVD-RW
      • The letters RW (Re-writable) means that the disk can be recorded over again and again
      • Unlike CD/DVD-R, this disk does not become ROM
      • The dye used to record data is special and allows bumps of data to be undone (which erase the data)
      • Data can be added to the disk and can also be erased
      • Uses
        • Used to record TV programs and can be recorded over many times
        • Used in CCTV cameras to keep on an eye on business and what is happening on the streets. CD/DVD-RW is perfect for these uses, as they can be updated over and over
      • Advantages
        • Can be reused many times
        • Not as wasteful as the CD/DVD-R format as if the burning fails, the disk can still be recorded onto later and not thrown away.
      • Disadvantages
        • More expensive to buy than CD/DVD-R disks
        • It is possible to accidentally overwrite data (since RW disk can be updated)
    4. DVD-RAM
      • Also known as DVD RAM.  It is a new addition to the optical media group.
      • Reading and writing data can happen at the same time
      • This means that you could watch a program while another is being recorded.
      • Can store up to 4.7 GB of data
      • Uses a similar phase changing recording dye to CD or DVD-RW which allows DVD-RAM disks to be recorded over many times.
      • Data can be reliably stored on DVD-RAM for many years due to their high quality
      • Uses
        • Because DVD RAM are so reliable, they are used in video and data archiving (safe store for important files and record).
        • Used in recording devices such as satellite receivers (such as Sky TV) to allow simultaneous recording and playback.
        • Used in camcorders to store films (reliably and for many years).
      • Advantages
        • Long life – last at least 30 years
        • Can be written over 10,000 times (RW disks allow 1,000 re-writes)
        • Very fast access to store files
        • Offer very large storage capacities compared to CDs (up to 4.7 GB)
        • Can read data at the same time its being written
      • Disadvantages
        • Pretty expensive.  Cost many times more than DVD-RW disks
        • Don’t work in many devices as he R and RW disks
    5. Bluray
      • Largest capacity of all the optical media.  They can sore up to 100 GB of data.
      • Work in a similar way to DVD ROMs but the laser used write/read data is blue rather than Red (Red lasers are used to read other disk types)
      • Blue lasers are capable of reading  data dots that are positioned closer together on the disk.  As a result data can be stored and read.
      • The blue laser is why the name ‘Blu-Ray’ was used
      • More data dots means higher capacity (50 million pages of text).
      • Blu ray – RW disks can be re-written in much the same way as RW disks.
      • Uses
        • Used to store HD video (like high quality movies).
        • Used in some home video consoles (like PS3).
        • Used to back up hard disk drives in PCs.
        • Camcorders use bluray disk to store large amounts of high quality footage.
      • Advantages
        • Huge storage capacity – Perfect for high quality movies
        • Data can be read/transferred very fast when compared to other optical media.
      • Disadvantages
        • Blu ray disks are very expensive compared to other types of disks.
        • Only work in blu ray drive/players which are expensive (which means that not many people have them which limits the use of the disks
    6. Solid State Storage
      • Solid State Storage have no moving parts.
      • No reels of tape, no spinning disks, no moving laser beams, etc.
      • Solid State Storage technology is known as ‘Flash Memory’ and examples include Memory Sticks, Pen drives and Memory Cards.
      • They store data as 1s and 0s (zeros) (just like magnetic and optical storage devices) within millions of mini transistors instead of on films of magnetic substance.
      • If the transistor conducts an electric current, this equates a 1.  If it does not conduct a current, this equattes a 0 (zero).
      • They hold several advantages over magnetic disk drives.
        • Smaller physical size
        • Consume much less power (No moving parts to use energy).
        • Much faster data access/transfer times.
        • More robust (No moving parts that makes them harder to damage)
      • Memory Stick
        • Memory sticks are small portable external storage devices.
        • Can be used to transfer/backup many GB of data/files between computers.
        • Memory sticks use Solid State technology and are usually connected to the computer via USB ports.
        • These are making other forms of portable storage (like CD’s and DVD’s) redundant as they are simply much easier and quicker to transfer data.
        • Data can be quickly read (used) or written (update) to the drive.
        • Memory sticks used be very expensive initially but they have become very cheap now.
        • Uses
          • Used for easily transporting files or data between PCs.
          • Used for backing up data quickly and easily.
          • Can be used as a security device (a dongle) to prevent software piracy.
        • Advantages
          • Very small and easy to transport data.
          • Robust and not easily damaged (no moving parts).
          • Work in any PC using USB connectivity.
        • Disadvantages
          • No write protect feature.  This means that it is possible to accidentally copy over data.
          • Small physical size means that they are easy to misplace or lose.
    7. Secure Digital Cards
      • These are in the form of Electronically Erasable Programmable Read Only Memory (EEPROM).
      • They are known as SD cards (Secure Digital).
      • These are Solid State Storage devices.
      • Micro SD cards are smaller version of the normal SD card.
      • Maximum capacity SD is 64 GB and maximum capacity of Micro SD is 32 GB.
      • Uses
        • Used to store photos in digital cameras.
        • Used in mobile phones as memory cards.
        • Can be used by MP3 players to store music files.
        • Used in hand held devices (like PDA) to store files and data.
      • Advantages
        • Very small so they are easy to transport files from one device to another (camera to camera for example).
        • Robust and not easily damaged (as there are no moving parts).
        • Easy to connect to devices through SD slots.
      • Disadvantages
      • More expensive per GB when compared to HDD.
      • Lower storage capacity than HDD.
      • Small size makes them quite easy to lose.
      • Have a limited number of times that they can be read/written to.
    8. High Definition DVD
      • It can hold around 150 GB of data (dual layer can hold twice than that).  HD DVDs are random access devices.  They are used in the same way as DVD ROMs, but since can hold more data, they are also used to store very high quality (HD) videos.  The HD-DVD format was launched at the same time as bluray.  For about a year, they competed to be the next DVD.  For various reasons, they failed to take off.
    9. Smart Card
      • Many credit cards (chip and pin cards), door entry cards, satellite cards have replaced the very limited storage of the magnetic strip with FM.  This is more reliable and has a much larger storage capacity.  Cards with flash memory are called smart cards.

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