1.3 Storage Flashcards
Why is secondary storage needed?
- Main memory is volatile
* Secondary storage is used to retain a copy of programs and data that need to be kept long term
What is a storage device?
A storage device is the physical hardware that carries out the storage action.
Give three examples of storage devices
- DVD writer
- Hard disk
- Solid State Drive
What is storage media?
Storage media is the physical object used to store the data
Give two examples of storage media
- DVD
* A magnetic tape cartridge
Name two secondary storage devices with no seperate media
A hard disk or a Solid State Drive are self-contained with no external media.
How does magnetic storage store data?
It uses minute particles or ‘domains’ to store data.
Give two examples of magnetic storage
- Magnetic Disk (e.g. Hard disk)
* Magnetic tape
What are 5 advantages of magnetic storage?
- Huge capacity (up to several terabytes)
- Low cost/gb (tape is cheapest, hard disk very low as well)
- Hark disk offers high speed data access
- Hard disk offers random access to data
- Magnetic tape can hold its data for up to 30 years
What are 5 disadvantages of magnetic storage?
- Not very portable
- Has mechanical moving parts - not as rugged as solid state storage
- Data can be lost/corrupted near strong magnetic fields
- Magnetic tape uses serial data access so is very slow
- Read/write not as fast as flash technology
List three examples of optical storage
- CD
- DVD
- Blu-ray disks
How are optical disks encoded with data?
- A laser beam burns tiny dark pits on to the surface of the optical disk.
- If a pit is present, this can represent a ‘1’.
- If no pit is present, this can represent a ‘0’.
What are 4 advantages of optical storage?
- Cheap for under 10GB
- Very portable compared to hard disk
- Ideally sized for storing movies and videos
- Immune to magnetic fields
What are 5 disadvantes of optical storage?
- Not cheap if terabytes need to be stored
- Not as portable as Flash media
- Slow to write and much slower than hard disk to acess
- Easily scratched
- Cannot write over stored data
What is another name for solid state media?
Flash media
List three examples of Flash media
- USB memory sticks
- Solid state drives
- SDHC memory cards (as found in digital cameras)
How is solid state media encoded with data?
• Solid state media hold data using electronic switches
What are 5 advantages of solid state storage?
- Very portable in the form of SD cards and USB sticks
- Large capacity (especially solid state drive)
- Very tough and rugged - no moving parts unlike a hard disk
- Faster than hard disk to read/write data (no mechanical parts)
- Silent unlike hard disks
What are 2 disadvantages of solid state storage?
- Expensive compared to a hard disk of similar capacity
* Less durable than a hard disk - limited number of erase/write cycles
Roughly how many erase/write cycles can solid state storage go through before it wears out?
About 100,000
What is magnetic tape typically used for?
Data archiving
Which storage media would hold a 2 hour movie with three sound tracks (foreign languages) and bonus features?
CD, Single layer DVD, Double layer DVD
Double layer DVD (larger storage up to 8.5GB)
What does CD stand for?
Compact disk
What six things should be considered when choosing a storage media?
- Capacity
- Speed
- Reliability
- Portability
- Durability
- Cost
When choosing storage media, what does ‘speed’ mean?
How quickly data can be accessed from or written to the media
What is the difference between durability and reliability?
- Durability is how resistant (rugged) the media is to damage - e.g. knocks and scratches
- Reliability is the ‘shelf life’ of the media - how long it will retain data so it can be accessed reliably and without error
