1. Storage devices and media

2. What is backing up of data?
It’s the copying of files/data to a different medium (disk, tape, flash drive, etc) in case of a problem with the main secondary storage device.
Backups are often stored in a different place to the main storage.

3. Reasons why backups are made?
To safeguard against loss of data due to the failure of the original secondary storage device, hardware failure or possible corruption of files
To safeguard against damage caused by hackers
In case the files need to be used elsewhere
Don’t necessary guard against the effect of a virus

4. Types of access Serial access Field: a single piece of info
Record :one complete set of fields
File: a collection of records
Where data records are stored one after the other with no regard to the order; are read by starting at the beginning and reading through every record until you find the one that you want.
When the original magnetic tape(master file) needs updating, an additional tape(transaction file) is required. The transaction file contains all the new data to allow the master file to be updated.

5. Direct access
Is used with magnetic disks, optical media and solid state media.
The computer uses the key field to calculate where data should be stored. It is then able to access the data directly from the calculated position.
Faster than serial access.

6. Secondary storage media
All systems have come equipped with some form of secondary storage.
Ensure that data is stored permanently so that it can be used again later on.
Storage/file sizes are measured in kilobytes, megabytes, gigabytes and terabytes.

7. Magnetic storage media

8. Magnetic storage media
Depend on the magnetic properties of certain materials.
Magnetic materials is coated on the surface of a disk or tape
Many hard disk drive are made up of more than one disk and these disks are known as platters.
Each platter is made from glass, ceramic or aluminium coated in a nickel alloy that can be magnetised

9. Fixed/internal hard disk drive (HDD)
The main method used for data storage
Uses: to store the operating system, systems software and working data; storing applications software that needs fast retrieval and storage of data
Advantages: fast data transfer rate, fast access times to data
Disadvantages: can be easily damaged, many moving parts when compared to solid state drives, can be quite noisy

10. Portable hard disk drives
Work in much the same as fixed hard disk drive but are usually connected to computers via the USB port; can be disconnected and used on different computers
Uses: used as backup systems to prevent loss of data, to transfer data/files/software between computers
Advantages: fast data access time and data transfer rate, large memory capacity, used as method of transferring info between computers
Disadvantages: can be easily damaged if dropped or subjected to a strong magnetic field

11. Magnetic tapes
Uses: in applications where batch processing is used, backup media since all the data needs to be stored, used in long-term archiving of data
Advantages: less expensive than hard disk, huge data, data transfer rate is fast
Disadvantages: slow data access time, when updating another tape is needed to store the final updated version, are affected by magnetic fields.

12. Optical storage media

13. CD/DVD disks
Laser light is used to red data and to write data on the disk’s surface.
Uses a thin layer of metal alloy or light-sensitive organic dye to store data
Data is stored in pits and bumps on the spiral track
Can be designed as:
-R: write once only
-ROM: can only be read
-RW: can be written/read from many times

14. CD-ROM and DVD-ROM Are ROM
Data is stored as a series of pits and lands in the metallic optical layer
Uses: store music files, software, games and reference software
Advantages: hold far more data than floppy disks, less expensive than hard disk drive
Disadvantages: data transfer rate and data access time is slower than hard disks

15. CD-R and DVD-R The letter R means the disk is recordable once only.
A thin layer of an organic dye is used as the recording media
Uses: home recording music and films, store data to be kept for later use or to be transferred to computers
Advantages: cheaper than RW disks, once burned and finalized they are like a ROM
Disadvantages: Not all CD/DVD players can read it, if finalized, it can only be recorded on once

16. CD-RW and DVD-RW
RW means these disks are a rewritable media and can be written over several times.
They don’t become ROM’s
Uses: record television shows, not as wasteful as R format as more data can be added, used in CCTV systems
Advantages: can be written over times, can use different file formats each time it’s used
Disadvantages: can be expensive, possible to accidentally overwrite data

17. DVD-RAM Allow numerous read and write operations
Can be read from and written to many times
Uses: recording devices such as satellite receivers to allow simultaneous recording and playback
Advantages: long life, possible to rewrite operation over times, fast access, large capacity
Disadvantages: many systems won’t recognise it, expensive, have been superseded by newer technologies

18. Blu-ray discs
Uses: home video consoles, storing and playing back movies, PCs can use it for data storage or backing up hard drives
Advantages: large storage capacity, fast data transfer rate, fast data access speed
Disadvantages: expensive, encryption problems

19. The future of optical media
Many computer systems now come with USB connectors only and no CD/DVD drives
The main method of transferring files has become flash memory
Many people now store their music in:
-hard disk drive systems
-in MP3 format on: computers, tablets, phone, portable music player
-using the cloud so they can access from anywhere
-by streaming their music from internet

20. Solid State Storage Media

21. Solid state drives (SSD)
SSDs are rapidly taking over HDDs
Have no moving parts and all data is retrieved at the same rate no matter where it is stored
The most common type of SSD devices store data by controlling the movement of electrons within NAND chips
Advantages: light, lower power consumption, thin because of no moving parts, fast data access

22. Memory stick/pen drives
Can store several gigabytes of data
Usually connected to a computer through USB port
Power to operate them is drawn from the host computer
Uses: transporting files between computers, backup store, used as a security device to prevent software piracy
Advantages: small, portable, doesn’t need additional software to work, not affected by magnetic fields
Disadvantages: can’t write-protect data/files, easy to lose

23. Flash memory cards
Uses: store photos on digital cameras, mobile phone memory cards, used in MP3 players, backup store in hand-held computer devices
Advantages: compact, easy to remove and used in another device, robust
Disadvantages: expensive, have a finite life regarding the number of times they can be read from or write to, lower storage capacity than hard disks