Optical Storage
Computer Science: Cambridge International GCSE, topic 1.3.13
How Optical Storage Works
Optical storage uses laser light to retrieve data from the surface of optical media. Optical storage is often used to deliver multimedia content such as video.
Storing a bit
- Each 1 or 0 (value of a bit) is represented as a microscopic hole (called a pit) or a flat surface (called a land) on the surface of the disk.
Accessing data
- A laser is shone on the disk surface.
- If the laser hits a land, it will be reflected into a sensor.
- If the laser hits a pit, then it will be reflected elsewhere.
- These can be used to represent our 1 and 0.
Properties of Optical Media
Optical media provides cheap and robust secondary storage.
Low cost
- Optical media is very cheap per-gigabyte (GB).
Great reliability
- Optical media is:
- Waterproof.
- Shockproof.
- This makes it ideal for portability (transporting).
Low capacity
- Each disk has a low capacity.
- Disks are small and fairly cheap. So it can be easy to gain a high capacity of storage by buying multiple disks.
Low speed
- Because the parts in the optical media drive have to move to find the right bit of data on the disk, access times can be quite slow.
- Writing to a disk can also be a very slow process.
Test yourself on Optical Storage
Does optical media tend to be cheap or expensive on a per-GB basis?
What is the most important factor that allows optical media to be transported?
Is it generally quicker to write data or read data on optical media?
I live in an area prone to flooding and need to make a backup of important files. Should I make a backup using magnetic, solid state, or optical media?