Storage Flashcards
What is the definition of primary storage and what are the three types?
Any storage directly accessed by the CPU
RAM, ROM and Registers/Cache
Why is primary storage (PS) needed?
It’s much faster to access data from PS than SS
What are the characteristics of RAM?
Random Access Memory
- Volatile - All data lost when computer turns off
- The computer’s working memory
- Can be written to, and read from
What are the characteristics of ROM?
- Non-volatile - data permanently on disk
- Used for computer’s start-up instructions (Bootstrap)
- Read-only - can’t be changed
Why is secondary storage necessary?
Needed for longer term storage of data because it is non-volatile.
External devices are also portable and can have large capacities
What are the benefits of an SSD compared to other forms of secondary storage?
Solid State Drive
Require little power and generate little heat
Lack of moving parts, therefore small, reliable and portable
Much faster than hard disks, and don’t require cooling equipment
What are the benefits of an HDD compared to SSDs?
Hard Disk Drive
Cheaper than SSDs
What are the uses of CDs and DVDs?
Short/medium term storage of music/video
Can last 10-25 years
How do SSDs work?
- Microscopic transistors act as control gates and floating gates to control the flow of the current
- Current flowing = 1
- No current = 0
- Use NAND or NOR gates
How does an optical drive work?
CD / DVD / Blu-Ray
- A laser reflects light off the surface of a disk with a spiral track of lands and pits
- When the laser hits the the curved start/end of a pit, the light is refracted and a 1 is recorded
- When light is reflected either from the land or pit, a 0 is recorded
Describe the operation of a hard disk drive
- Hard disks are magnetic surfaces divided into tracks and sectors
- They rotate around a spindle and a read/write head is moved onto the correct track
- Particles on the magnetic disk are polarised (north = 0, south = 1)
- The read/write head must be parked once operation is finished, otherwise it will break
When is virtual memory used?
When there isn’t enough space in RAM for all of the programs and data that are being used
Describe the process of virtual memory
- Small section of hard drive reserved to act like RAM
- When program in VM is needed, it is swapped with something in RAM
- This could cause your computer to slow down as it is a further distance to get to hard drive than to RAM
What is cloud storage?
Remote file storage on someone else’s servers.
Often done with major third-party companies.
What is important to remember about cloud storage?
Physical devices are still needed to store data in cloud storage
