Secondary Storage II
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- Compare the capacity, speed and portability of magnetic, optical and solid-state storage devices
- Select an appropriate type of storage for a particular purpose
- Construct an expression to calculate data storage requirements.
Recap
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Last lesson you learned about the three types of storage: magnetic, optical, and solid state.
You learned about how they work and looked at some of the basic pros and cons of each.
Today, you are going to examine in detail the differences between the three types and discuss why you would choose one over the others in specific situations.
Activity 1
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You will need to read it carefully to extract the part that corresponds to the questions in the first column.
Research examples of the three types of storage devices and complete the table below. You can find most of the information you need on this webpage:
For information on magnetic tapes, you can visit this webpage:
Things to consider
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You need to think about the criteria you will use for comparison, before you actually do the work.
You need to consider the following aspects of each type of data storage:
- capacity – how much data can the device store?
- portability – can the device be moved around without damaging it or the data it contains?
- speed – how fast can data be read from and written to the device?
Activity 1
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| Optical | Magnetic | Solid State | |
|---|---|---|---|
|
Capacity How much data can this device store? Note the average capacity or give a range. |
|
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Portability Can the device be moved around with no damage to the data it contains? Why might damage be caused? |
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Speed How quickly can data be read from the device? How fast can data be written to the device? Why is this the case? |
CDs: 640 MB
DVDs: 4.7 GB
Blu-ray: 50 GB
Hard drives:
500 GB – 12 TB
Tape:
Up to 15 TB per tape
Solid state drives: 256 GB – 4 TB
USB memory sticks: 2 GB – 2 TB
Very portable
Internal hard drives: fixed
External drives: portable
Tape: Very portable
Internal hard drives: fixed
External drives: portable
CDs: very slow
DVDs: slow
Blu-ray disks: slow
Hard drives:
slow
Tape drives:
very slow
Solid state drives:
very fast
USB memory sticks:
fast
Choosing a device for a scenario
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For example:
Now that you know a lot about the different types of data storage technology, you need to be able to choose the most appropriate type to use for a given situation.
Your school has a small handheld video camera that a group of students need to use for Geography fieldwork. What would the most appropriate storage type to use with the camera and why?
Answer:
A solid state memory card would be most appropriate. It would have a large enough capacity for video files and could be added to with additional memory cards. Such cards have a high write speed, which will support more data being read to the storage medium, and allow students to film in high quality. They are also highly portable – memory cards are small and have no moving parts that can be broken.
Activity II
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An international software development company has a local division with 3,400 employees.
Currently, they are working on developing a new application that can analyse data from the Internet of Things sensors on jumbo jets.
Approximately a tebibyte of data is collected per flight.
The company is looking for:
- a way to store the data while it is being analysed
- a way to store it when it is no longer needed in the live system.
Activity II
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An international software development company has a local division with 3,400 employees.
Currently, they are working on developing a new application that can analyse data from the Internet of Things sensors on jumbo jets.
Approximately a tebibyte of data is collected per flight.
The company is looking for:
- a way to store the data while it is being analysed
A solid-state drive (SSD) would be well suited for this application because it can read and write large volumes of data at speeds of up to 3 GiB per second, making it ideal for analysing flight data quickly
Activity II
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An international software development company has a local division with 3,400 employees.
Currently, they are working on developing a new application that can analyse data from the Internet of Things sensors on jumbo jets.
Approximately a tebibyte of data is collected per flight.
The company is looking for:
- a way to store it when it is no longer needed in the live system.
Tapes provide low-cost, high-capacity data storage which makes them ideal for long-term data archiving and backup. Their slow write/retrieval rate isn’t an issue in this case, since the data is not needed in the live system. Capacity is the main issue. You can keep adding tapes, so capacity is almost unlimited.
Activity II
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For each of the following situations, state which storage type would be the most appropriate and explain why.
Media students have taken part in a national competition. Each has produced a one-hour high-definition video of an original screen play.
The judges for the competition are in different parts of the country and each will do a pre-screening of a subset of entries. They are willing to accept any type of media.
The competition sponsors have asked that all submissions be sent through the post, directly to one of the judges.
Name and give a justification for a way to send the submission by physical post to the judge.
Activity II
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Media students have taken part in a national competition. Each has produced a one-hour high-definition video of an original screen play.
The judges for the competition are in different parts of the country and each will do a pre-screening of a subset of entries. They are willing to accept any type of media.
Name and give a justification for a way to send the submission by physical post to the judge.
The file size of the video is likely to be about 3-4 GiB. The capacity of a DVD is more than sufficient to hold such a video.
DVDs are cheap to buy and strong enough to be sent through the post.
Alternatively, students could use a high-capacity flash drive (memory stick). The advantage of using a flash drive is that there would be no need to have a dedicated peripheral device to record/view the video. However, using a memory stick for this purpose would be considerably more expensive than using a DVD. There is also a greater likelihood of a memory stick being damaged in transit.
Activity II
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For each of the following situations, state which storage type would be the most appropriate and explain why.
A group of students is working on a monthly college newsletter. Due to other activities, four of the group did not have time to complete their sections at school, so must complete them at home.
Unfortunately, the college does not allow access to students’ file storage from home.
Name and give a justification for a way that the students can carry the newsletter files and finish their sections of the newsletter at home.
Activity II
P03d
A group of students is working on a monthly college newsletter. Due to other activities, four of the group did not have time to complete their sections at school, so must complete them at home.
Unfortunately, the college does not allow access to students’ file storage from home.
Name and give a justification for a way that the students can carry the newsletter files and finish their sections of the newsletter at home.
A flash drive (memory stick) would be the best way to take the newsletter files home. Flash drives are lightweight and portable and would have sufficient capacity to hold the files.
Most laptops, even old ones, have USB ports where a USB drive can be inserted, so no other device is required.
Files can then be worked on either directly on the USB drive or uploaded to the hard disk of each student’s laptop. Files can be copied back to the USB drive when they have been updated and they need to be taken back to school.
Capacity
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Until recently, standard decimal prefixes – kilo, mega, giga, etc. – have been used to represent binary multiples. This has caused some confusion.
To address this, the International Electrotechnical Commission (IEC) has produced a set of binary prefixes to represent binary multiples.
These are the units of measurement you are expected to use for data storage and memory capacity.
| Unit | Abbreviation | Bytes | Equivalent to |
|---|---|---|---|
| bit | 1 bit |
||
| nibble | 4 bits |
||
| byte | 20 bytes | 8 bits or 2 nibbles |
|
| kibibyte | KiB | 210 bytes | 1024 bytes |
| mebibyte | MiB | 220 bytes | 1024 kibibytes |
| gibibyte | GiB | 230 bytes | 1024 mebibytes |
| tebibyte | TiB | 240 bytes | 1024 gibibytes |
Binary multiples
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Conversion between the units is straightforward.
Example
A hard disk has a storage capacity of 1.5 TiB. Express this in:
- mebibytes
- Kibibytes
1TiB = 1024 MiB so
1.5 TiB = 1024 * 1.5 MiB
1MiB = 1024 KiB so
1.5 TiB = 1024 * 1024 * 1.5 KiB.
Exam note:
You are not allowed a calculator in the exam.
This means you are not expected to actually calculate the answers to questions like this.
Instead you should construct an expression to show how the answer would be calculated
Review
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Compare the capacity, speed and portability of magnetic, optical and solid-state storage devices.
- Capacity is measured in mebibytes, gibibytes and tebibytes.
- Speed refers to how fast data can be written to and read from a device.
- Portability means how much movement the device can be subjected to without causing damage to the device or the data it contains.
p03e Secondary Storage II
By David James
p03e Secondary Storage II
- 384
