Backing Storage

1. Backing Storage

2. Backing Storage Devices • Backing storage devices allow us to store programs and data so that we can use them later • Backing storage devices can be split into 4 categories: • Magnetic (Hard Disk Drive) • Optical (CD, DVD, Blu-ray) • Solid State (Solid State Drive, USB Flash Drive) • Hybrid (Hard Disk + Solid State Drive)

3. Hard Disk • Solid disk (made of metal or very hard plastic) • Usually permanently fixed inside the computer (or close by it in its own box) • Large capacity • Data is stored magnetically

4. Optical Storage (CDs and DVDs) • Data is stored on surface of the CD or DVD in a series of pits • Pits are read by shining laser light onto the surface of the disk. • CDs and DVDs rotate at a very high speed and the laser beam is reflected off the disks surface.

5. CD-ROM • Data cannot be writtento CD ROM once it has been produced • Data is usually written on a CD-ROM in a factory (where it is being made/produced)

6. CD-R (Recordable) • Data is written onto the disk using a special disk drive unit. • The unit burns a permanent pattern into the surface of the disk using a high precision laser beam. • CD-R disks can only be written to until the disk is full

7. CD-RW (Rewriteable) • Data is written and rewritten onto the disk using a special disk drive unit. • The unit uses a high powered laser beam with 3 states • High – used to record data • Medium – used to erase data • Low – used to read the data • CD-RW (CD-Rewritable) disks can be written and rewritten many times

8. DVD ROM • Stores greater amounts of information than a CD • A DVD can store more information because: • Pits are smaller • Can have two layers on each side and be double sided • DVD-ROM cannot be writtento once it has been produced

9. DVD-R & DVD -RW • DVD-R and DVD+R (Recordable) • Write once medium • Disk can only be written to until the disk is full • DVD-RW (Rewritable) • Disks can be written and rewritten many times

10. Blu-ray Disk (BD) • Stores an even greater amount of information than DVDs • A Blu-ray can store more information because: • Pits are even smaller • Can have up to 4 layers on one side • Disk is read by a shorter wavelength blue laser

11. BD-R and BD-RE • BD-R (Recordable) • Write once medium • Disk can only be written to until the disk is full • BD-RE (Rewritable) • Disks can be written and rewritten many times

12. Solid State Drive • A solid state drive stores information on memory chips • There are no moving parts which means: • Data can be accessed very quickly • Less power is consumed • More robust than hard disk • More expensive and much smaller capacity than a hard disk drive

13. USB Flash Drive • USB – Universal Serial Bus • Device used to store data, such as pictures and movie files • USB Flash Driveis a Solid State Device as there are no moving parts

14. Hybrid Drive • A mixture of a hard disk drive and a solid state drive • Frequently accessed data is stored on the faster to access solid state part • Has large storage capacity advantage of a hard disk, and quick access advantage of a solid state drive

15. Calculating Storage • How many 3Mb photos would fit on a 4Gb flash card? • How many 50Mb tracks would fit on a CD?