Revision Library

revisionlibrary.co.uk

GCSE · Computer Systems - Storage

P1.3 Secondary Storage

OCR J277 · Calculators not allowed · about 80 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

Secondary storage is used in a huge range of computer systems, from smartphones to supercomputers.

(a)State what is meant by the term 'secondary storage'.(1)

(b)Give two examples of secondary storage devices.(2)

(c)State one reason why a computer needs secondary storage as well as RAM.(1)

(Total for Question 1 is 4 marks)

Complete the table below by identifying whether each storage device mainly uses magnetic, optical or solid-state technology.

1. Hard disk drive (HDD)
2. DVD-RW
3. USB flash drive
4. Blu-ray disc
5. Solid-state drive (SSD)
6. Magnetic tape

(Total for Question 2 is 6 marks)

Optical storage media come in several formats, each with a different maximum capacity.

(a)State the typical maximum storage capacity of a standard single-layer CD.(1)

(b)State the typical maximum storage capacity of a single-layer DVD.(1)

(c)State the typical maximum storage capacity of a single-layer Blu-ray disc.(1)

(Total for Question 3 is 3 marks)

Answer the following multiple-choice questions about secondary storage.

(a)Which of these is an example of optical storage?(1)

A) Solid-state drive (SSD)
B) Blu-ray disc
C) Magnetic tape
D) RAM

(b)Which characteristic best describes a solid-state drive compared with a magnetic hard disk drive?(1)

A) Uses spinning magnetic platters
B) Has a slower read/write speed
C) Has no moving mechanical parts
D) Has a lower typical cost per gigabyte

(Total for Question 4 is 2 marks)

Magnetic tape is still widely used by large organisations today.

(a)State one common use of magnetic tape in modern computer systems.(1)

(b)Give one advantage of using magnetic tape rather than hard disk drives for backing up data.(1)

(c)Give one disadvantage of using magnetic tape rather than hard disk drives for backing up data.(1)

(Total for Question 5 is 3 marks)

Put these units of data in order of size, starting with the smallest: gigabyte, byte, terabyte, kilobyte, megabyte

(Total for Question 6 is 2 marks)

Describe how data is stored on a magnetic hard disk drive (HDD).

(Total for Question 7 is 3 marks)

Describe how data is read from an optical disc such as a DVD.

(Total for Question 8 is 3 marks)

Explain why solid-state drives (SSDs) are generally more suitable than magnetic hard disk drives for use in laptops that are frequently carried around.

(Total for Question 9 is 3 marks)

Solid-state drives (SSDs) are increasingly used instead of magnetic hard disk drives.

(a)Explain how a solid-state drive stores data.(3)

(b)State two advantages of solid-state storage compared with magnetic storage.(2)

(Total for Question 10 is 5 marks)

A student's smartphone has 64 GB of free storage space. Each MP3 song file is on average 4 MB in size. Calculate the maximum number of songs that can be stored in the free space.

(Total for Question 11 is 3 marks)

A dashcam records video at a constant data rate of 8 megabits per second (Mbps). Calculate the amount of storage, in megabytes (MB), needed to store 15 minutes of continuous recording.

(Total for Question 12 is 4 marks)

A small shop owner is installing a CCTV system that records video continuously and automatically overwrites the oldest footage once the storage is full. Recommend a suitable type of secondary storage for the CCTV system's video recorder. Justify your answer by referring to at least two characteristics of storage.

(Total for Question 13 is 4 marks)

A games console manufacturer is designing a small, battery-powered, handheld games console. Recommend and justify the most suitable type of secondary storage for storing games and save data in this handheld console.

(Total for Question 14 is 4 marks)

A company backs up its files onto magnetic tape cartridges, each with a capacity of 2.5 TB. The company needs to back up 18 TB of data. Show that 8 tape cartridges are needed.

(Total for Question 15 is 3 marks)

A 2 TB hard disk drive (HDD) costs £45. A 1 TB solid-state drive (SSD) costs £75. Calculate the cost per gigabyte (GB) of each storage device, and state which device is cheaper per GB.

(Total for Question 16 is 5 marks)

A large company needs to store an archive backup of all its data. This archive is rarely accessed but must be kept safely for several years. Recommend a suitable type of secondary storage for this long-term archive backup, and justify your answer.

(Total for Question 17 is 4 marks)

A secondary school is upgrading its computing suite. The new computers will mainly be used for editing large, high-resolution video files. Discuss the suitability of magnetic, optical and solid-state storage for this computing suite, and recommend which type of storage the school should use. Justify your recommendation.

(Total for Question 18 is 6 marks)

A film production company records raw 4K video at a constant data rate of 400 megabytes (MB) per second. The company has an external storage array with a total capacity of 18 TB, of which 2 TB is already in use. Show that the remaining free space is enough to store 11 hours of raw 4K footage, but not enough to store 12 hours.

(Total for Question 19 is 5 marks)

Mark scheme · P1.3 Secondary Storage

Question 1

(a) B1 Non-volatile storage that holds data and programs permanently, even when the device is switched off oe
(a) Answer: Non-volatile storage that holds data/programs permanently, even without power.
(b) B1 First valid device, e.g. hard disk drive (HDD)
(b) B1 Second valid device, e.g. solid-state drive (SSD)/USB flash drive/DVD/Blu-ray disc/magnetic tape (any other valid device)
(b) Answer: e.g. hard disk drive (HDD) and USB flash drive (any two valid secondary storage devices).
(c) B1 RAM is volatile and loses its contents when the power is turned off, so secondary storage is needed to store data/programs permanently oe
(c) Answer: RAM is volatile (loses data when the power is off); secondary storage keeps data permanently.

Question 2

B1 1. Hard disk drive (HDD) - Magnetic
B1 2. DVD-RW - Optical
B1 3. USB flash drive - Solid-state
B1 4. Blu-ray disc - Optical
B1 5. Solid-state drive (SSD) - Solid-state
B1 6. Magnetic tape - Magnetic
Answer: 1 Magnetic, 2 Optical, 3 Solid-state, 4 Optical, 5 Solid-state, 6 Magnetic

Question 3

(a) B1 700 MB (accept 650 to 700 MB)
(a) Answer: 700 MB
(b) B1 4.7 GB
(b) Answer: 4.7 GB
(c) B1 25 GB
(c) Answer: 25 GB

Question 4

(a) B1 B
(a) Answer: B) Blu-ray disc
(b) B1 C
(b) Answer: C) Has no moving mechanical parts

Question 5

(a) B1 Backing up/archiving large amounts of data held by an organisation oe
(a) Answer: Long-term backup/archiving of large volumes of organisational data.
(b) B1 Much lower cost per gigabyte for very large capacities oe / very high capacity available
(b) Answer: Lower cost per GB for very large capacities.
(c) B1 Data must be accessed sequentially, so it is much slower to locate/retrieve a specific file oe
(c) Answer: Slow sequential access, so retrieving a specific file takes much longer.

Question 6

B1 At least 3 of the 5 units placed in the correct relative order
B1 All 5 units placed in the fully correct order cao
Answer: byte, kilobyte, megabyte, gigabyte, terabyte

Question 7

B1 The disk has one or more platters coated in a magnetic material
B1 A read/write head moves across the surface of the spinning platter(s)
B1 The head magnetises tiny areas of the surface in different directions to represent binary 1s and 0s oe
Answer: Platters coated with magnetic material are spun at high speed; a moving read/write head magnetises small areas of the surface in one of two directions to represent 1s and 0s.

Question 8

B1 A laser is shone onto the surface of the spinning disc
B1 The disc surface has raised areas (lands) and indentations (pits)
B1 Pits and lands reflect the laser light differently; a sensor detects this difference in reflection and converts it into binary data (1s and 0s) oe
Answer: A laser scans the spinning disc; pits and lands on the surface reflect the light differently, and a sensor converts these differences into binary 1s and 0s.

Question 9

B1 SSDs have no moving mechanical parts oe
B1 so they are less likely to be damaged/fail if dropped or knocked, unlike an HDD whose spinning platters and read/write head can be damaged by physical shock oe
B1 SSDs typically use less power and are lighter, which suits a portable, battery-powered device oe
Answer: SSDs have no moving parts, so are far more resistant to physical shock than HDDs, whose spinning platters and head can be damaged if dropped; SSDs also use less power, extending battery life in a portable laptop.

Question 10

(a) B1 Data is stored electronically in flash memory/NAND memory chips oe
(a) B1 There are no moving mechanical parts oe
(a) B1 Data is stored as electrical charges in memory cells, representing binary values oe
(a) Answer: SSDs store data electronically in flash memory chips, using electrical charges in memory cells to represent binary 1s and 0s, with no moving parts.
(b) B1 Faster read/write access speeds oe
(b) B1 More durable/robust as there are no moving parts to be damaged by shock oe (accept: silent operation / lower power consumption)
(b) Answer: Faster access speeds; more durable/robust because there are no moving parts.

Question 11

M1 Converts 64 GB to MB: 64 x 1000 = 64000 MB oe
M1 Divides total MB by song size: 64000 / 4
A1 16000 (songs) cao
Answer: 16000 songs

Question 12

M1 Converts megabits per second to megabytes per second: 8 / 8 = 1 MB per second oe
M1 Converts 15 minutes to seconds: 15 x 60 = 900 seconds
M1 Multiplies data rate by time: 1 x 900
A1 900 MB cao
Answer: 900 MB

Question 13

B1 Identifies a suitable storage device/technology, e.g. hard disk drive (HDD) oe (any storage type accepted if justified)
B1 Valid justification point 1, e.g. large/high capacity needed to store continuous video footage oe
B1 Valid justification point 2, e.g. relatively low cost per gigabyte for the large amount of storage required oe
B1 Valid justification point 3, e.g. can reliably cope with being written to/overwritten continuously, with adequate write speed for continuous video oe
Answer: A hard disk drive (HDD): high capacity and low cost per GB suit continuous video recording, and it can withstand being written to and overwritten repeatedly.

Question 14

B1 Identifies solid-state storage (e.g. flash memory/SSD/microSD)
B1 Valid justification point 1, e.g. no moving parts, so more resistant to damage if dropped/knocked while carried around oe
B1 Valid justification point 2, e.g. smaller and lighter, suiting a compact handheld device oe
B1 Valid justification point 3, e.g. lower power consumption, extending battery life, or faster loading times oe
Answer: Solid-state storage: no moving parts makes it shock-resistant, and it is small, light and uses less power, extending battery life.

Question 15

M1 18 / 2.5 = 7.2 (cartridges)
M1 Recognises that a cartridge cannot be shared/part-used, so the number of cartridges must be rounded up to the next whole number
A1 8 cartridges, cso (printed answer must be reached by a correct method)
Answer: 8 cartridges

Question 16

M1 Converts 2 TB to GB: 2 x 1000 = 2000 GB
A1 HDD cost per GB = 45 / 2000 = £0.0225 per GB awrt
M1 Converts 1 TB to GB: 1 x 1000 = 1000 GB
A1 SSD cost per GB = 75 / 1000 = £0.075 per GB awrt
B1 ft States the HDD is cheaper per GB, consistent with their two calculated figures
Answer: HDD = £0.0225 per GB; SSD = £0.075 per GB; the HDD is cheaper per GB.

Question 17

B1 Identifies magnetic tape as a suitable storage technology
B1 Valid justification point 1, e.g. much lower cost per gigabyte than other media for very large capacities oe
B1 Valid justification point 2, e.g. long shelf life, suiting long-term archival storage oe
B1 Valid justification point 3, e.g. slower sequential access speed is an acceptable trade-off since the data is rarely accessed oe
Answer: Magnetic tape: very low cost per GB for huge capacities and a long shelf life make it ideal for rarely-accessed, long-term archives, and its slow sequential access is not a problem since the data is not needed quickly.

Question 18

Level 1 (1-2): Basic, generalised statement(s) about one or more storage types, with little or no reference to the video editing scenario. A recommendation may be missing, unclear or unjustified. Little or no use of appropriate technical terminology.
Level 2 (3-4): Some relevant discussion of at least two storage types, referring to characteristics such as capacity, speed or cost, with limited application to the video editing scenario. A recommendation is given, but the justification is only partially linked to the scenario. Some appropriate technical terminology is used.
Level 3 (5-6): A detailed, well-structured discussion of all three storage types (magnetic, optical and solid-state), clearly applying relevant characteristics (e.g. capacity, speed, cost, durability, portability) to the video editing scenario. A clear, well-justified recommendation is given that is fully supported by the discussion. Appropriate technical terminology is used throughout.
Indicative content:
- Magnetic (HDD): low cost per gigabyte and high capacity, but slower read/write speeds than solid-state, which may affect smooth editing/scrubbing of large video files
- Magnetic (HDD): has moving parts, so is more prone to mechanical failure and is less shock-resistant
- Optical (DVD/Blu-ray): relatively low capacity and slow read/write speed compared with the file sizes involved in video editing; more suited to distributing finished video than to active editing
- Solid-state (SSD): much faster read/write speeds, allowing smoother playback and editing of large, high-resolution video files
- Solid-state (SSD): no moving parts, so more durable/reliable, but typically more expensive per gigabyte than magnetic storage, so may offer less capacity for the same budget
- A justified recommendation, e.g. SSD, or a combination of SSD for active project files and HDD for archiving completed work, weighing speed benefits against cost/capacity

Question 19

M1 Free space = 18 - 2 = 16 TB, converted to 16,000,000 MB (16 x 1000 x 1000)
M1 Data recorded per hour = 400 x 3600 = 1,440,000 MB
M1 11 hours = 11 x 1,440,000 = 15,840,000 MB, which is less than 16,000,000 MB, so 11 hours fits
A1 12 hours = 12 x 1,440,000 = 17,280,000 MB, which is more than 16,000,000 MB, so 12 hours does not fit
A1 cso: correct conclusion stated consistently with both given comparisons (11 hours possible, 12 hours not possible)
Answer: Free space = 16 TB = 16,000,000 MB. 11 hours needs 15,840,000 MB (fits, 160,000 MB spare). 12 hours needs 17,280,000 MB (does not fit, 1,280,000 MB short).

Secondary Storage - Worksheets, Questions and Revision