Storage devices and media Flashcards
Storage medium
Part of storage device that stores data
Storage device
Peripheral devices to main computer system and are used to hold data whether it is on or off. These machines let us store data on the medium and read from it
Three types of storage device
Magnetic storage media, optical storage media, solid state storage
Magnetic storage media
Hold data magnetically. Surface of device is magnetic. Data is written on it by changing local magnetic polarity to 1 or 0. magnetic device can extract data by reading magnetic state of disk
Optical storage media
Store data thanks to pits on surface burnt by laser, they present 0s or 1s. Laser can be shone onto these differences more gently and where it hits the pits, reflection is more different than it would be coming from a flat surface, differences used to store digital data
Solid state storage
Different from magnetic and optical as it has no moving parts and fits directly into computer. Device and medium are the same thing. Uses only electronic circuits and flash memory
Read/write head
device on each type of disk that can store data on and we can read data from it.
Advantages of fixed hard disk
Fixed hard disks can
- can store v large amounts of data
- access to data is fast
- no limit for number of times medium can be resued (data deleted or rewritten)
Disadvantages of fixed hard disk
Fixed hard disks can be fragile, so data stored on them should be backed up for safety because they’re stored inside computer’s case
What type of data do fixed hard disks store?
- Operating system of computer
- User’s applications
- User’s data including any work user has done on computer and any files like music or videos that have been downloaded
Where are three types of storage data stored and sent
Stored on hard disk and sent to computer’s RAM
Why is storage data stored/organized on disk
So that direct access to it is possible.
Fixed hard disk
Main storage on most personal computers, stored on one or more disks, hard disk fixed in its drive in computer so it refers to both hard disk and hard drive at the same time
What is direct access to data
Every disk has index on its surface. User sends instruction to read particular file of data, read/write head looks for it in index and goes straight to that part of disk.
Portable/ removable hard disks
Not connected inside computer case and can be moved around. Usually have dif interface type to computer for ex. USB, need to be more protective than fixed drive as they’re likely to get knocked as they are moved about
Portable/removable hard disk advantages
- does not require external power source, unlike fixed hard drive, so you can connect it to USB and start using immediately
- small enough to carry around
- can be used easily by multiple PCs for file sharing, esp. large files
- allows scheduled automatic backup of files that is easy to set up, doesn’t matter if you forget backup
- allows quick data archiving
Portable/removable hard disk disadvantage
Not recommended to switch between PCs and Macs once disk is formatted
Magnetic tapes
Tapes that store data similarly to magnetic disks, except data is stored in a long line on the tape rather than scattered over surface of disk.
Magnetic tape drive
Device that drives tape around read/write heads. In this device heads stay still and tape moves past it. In magnetic storage media head moves.
Serial storage
In magnetic tape, read/write head will take a long time to reach far end because all other data will have to be read first.
** DATA IS STORED ONE PIECE AFTER THE OTHER **
Sequential storage
Faster than serial storage, data arranged in certain order ex. alphabetical, however still very slow compared to direct access to data on hard disks
When and why is tape storage used
When large amounts of data needs to be stored but speed of access isn’t important, ex storing backups where a lot of data needs to be stored.
Tape storage is cheaper and less likely to be corrupted
When is sequential storage useful?
- Payroll for an entire company; not one employee will be missed, everyone’s data HAS to be read. processed once a month
- Utility bills; need to be sent to every customer on particular dates
Optical storage media
CD (compact disk) DVD (digital versatile stick), both use laser to read data, however DVD uses a more precise laser which helps data be closer together and squeezed onto the surface
Storage media
Something onto which data is written for safekeeping, like a tape or a disk
It’s vital to distinguish between disks we can write to and those we can read, what are the main types?
ROM- read only memory, can’t be written to, only read from
R- recordable, can be written to just once and then only read from
RW- re-writable, can be written to multiple times
CD ROMs and DVD ROMs Advantages
- If contents need to be protected from being corrupted it can’t be changed, used often for music or movie sale
- Software companies use them to distribute software and data files, publishers to distribute reference material like encyclopedias
- large amount of data can be stored without being easy to damage
- fairly inexpensive
CD Rs and DVD Rs Advantages
- used for copy files, an archive etc..
- you can write what you want on them then material is protected
CD ROMs and DVD ROMs disadvantage
also a disadvantage that data cannot be changed, if someone is bored of a movie for ex, they cannot access anything new
CD Rs and DVD Rs Disadvantages
- Less useful for making regular backups
- As they can be written to only once, not all CD/DVD devices can play them
CD RWs and DVD RWs Advantages
- ideal for moving files from one computer to another, ex taking work to school you did at home
- not easy to damage
- store large amounts of data
- can be reused over and over again
- ideal for taking backups
CD RWs and DVD RWs Disadvantages
- since it stores a lot of data and this data can be rewritten, data is easier to steal
DVD RAM Advantage
surface can be written on more often than RW
- access to data is faster
- can read and write at the same time
- greater capacity
DVD RAM disadvantage
- cant be used in ordinary DVD player
- more expensive than other optical storage media
Blu-Ray disks
- can preform high speed transfers and have much larger storage capacities than other optical storage media
- can record and play back video in very HD
Blu- Ray disk disadvantage
- very expensive
Solid state storage devices
- have no moving parts
- similar tech to RAM and ROM but don’t need electricity
- small and portable, can store a lot of data
- straightfoward to use as many are designed to directly fit computer port
Memory stick and pen drive
two names for same thing
they are used for backups and transport of info from one device to another
Flash memory cards
- portable memory
- fits in usb port
- flat and looks like a card
- can be CF (computer flash) or SD (secure digital)
- used in small electronic devs
- store media.. movies, photos, etc
