Secondary Storage

1 State why a computer system requires secondary storage. 2

One mark for each of the following, to a maximum of 2.

• Secondary storage is non volatile
• So data and programs are kept when the computer is switched off, which RAM cannot do

Model answer. Secondary storage is required because it is non volatile, which means it retains its contents when the power is removed. RAM is volatile and loses everything when the computer is switched off, so files, applications and the operating system itself must be stored in secondary storage in order to survive between sessions.

2 Describe two differences between solid state and magnetic secondary storage. 4

One mark for each of the following, to a maximum of 4.

• Solid state has no moving parts, magnetic uses spinning platters and a moving read write head
• Solid state is faster to read and write
• Solid state is more durable and resistant to physical shock
• Magnetic is cheaper per gigabyte and often available in larger capacities

Model answer. The first difference is construction. Solid state storage uses flash memory with no moving parts, whereas magnetic storage uses rigid platters that spin at high speed with a read write head that moves across the surface. This leads directly to the second difference: because nothing has to move mechanically, a solid state drive reads and writes data significantly faster and is far more resistant to damage from being knocked or dropped. In exchange, magnetic storage is considerably cheaper per gigabyte and is typically available in larger capacities for the same price.

3 A film crew records video on location in remote areas. They need portable storage for the raw footage. Discuss which type of secondary storage they should use. 6

One mark for each of the following, to a maximum of 6.

• Recommends solid state storage
• Durability: no moving parts so it survives transport and rough handling
• Speed: video files are very large so fast write speed matters
• Portability: physically small and light to carry
• Power consumption is lower, useful when mains power is unavailable
• Acknowledges the higher cost per gigabyte as the trade off

Model answer. The crew should use solid state storage such as portable SSDs or high capacity memory cards. The most important factor is durability: they are working in remote areas and equipment will be carried, jolted in vehicles and used in poor conditions, and because solid state storage has no moving parts it is far less likely to be damaged by physical shock than a magnetic hard disk with spinning platters and a floating read write head. Speed is the second consideration, because raw video files are extremely large and a slow write speed would either drop frames during recording or leave the crew waiting a long time to transfer footage at the end of a shoot. Solid state devices are also physically small and light, which matters when everything has to be carried, and they draw less power, which is a genuine benefit when mains electricity is not available and everything is running from batteries. The clear trade off is cost, since solid state storage is significantly more expensive per gigabyte than magnetic storage, so the crew will pay considerably more for the same capacity. Given that losing footage would mean losing an entire shoot that cannot easily be repeated, the extra cost is justified.

4 Explain why optical storage might still be chosen for distributing software to customers. 3

One mark for each of the following, to a maximum of 3.

• Very cheap to produce in large quantities
• Read only versions cannot be modified or overwritten by the customer
• Discs are lightweight and easy to post or stock in shops

Model answer. Optical discs remain a reasonable choice for software distribution because they are extremely cheap to manufacture in large quantities, so the cost of producing many thousands of copies is very low. Read only formats also cannot be altered or overwritten by the customer, which protects the integrity of the software and prevents accidental modification. Finally, discs are thin, light and robust enough to be posted or stocked on shop shelves easily, which makes physical distribution straightforward.

5 A school has 500 desktop computers and needs to choose secondary storage for them. Students store documents and presentations only. Recommend a storage type and justify your recommendation. 5

One mark for each of the following, to a maximum of 5.

• Recommends magnetic hard disk drives
• Cheapest cost per gigabyte, important when buying 500 units
• Large capacity available for documents and presentations
• Desktop machines are not moved, so the durability weakness of magnetic storage does not matter
• Notes that documents are small files, so the speed advantage of SSD is not worth the extra cost here

Model answer. The school should choose magnetic hard disk drives. The dominant factor is cost, because buying storage for 500 machines multiplies any price difference five hundred times, and magnetic storage has by far the lowest cost per gigabyte. Hard disks also offer large capacities as standard, which comfortably exceeds what is needed for documents and presentations. The usual weakness of magnetic storage, its vulnerability to physical shock because of the spinning platters and moving head, is not relevant here because desktop computers sit permanently on desks and are not carried around. Solid state drives would boot and load faster, but student work consists of small documents and presentation files rather than large media, so the speed advantage would be barely noticeable in daily use and would not justify the substantially higher cost across the whole school.