LEARNING OBJECTIVES
Be able to identify the need for secondary storage
Be able to know the data capacity and calculation of data capacity requirements
be able to identify and explain the different types of storage devices.
Design a wix page template for Computer Science.
SUCCESS CRITERIA
Success Criteria:
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Explain the need for secondary storage.
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Describe common storage technologies such as optical, magnetic and solid state.
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Be able to select suitable storage devices and storage media for a given application
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Justify their choice using characteristics such as capacity, speed, portability, durability and reliability.
1.3 Secondary Storage
The need for secondary storage
• data capacity and calculation of data capacity requirements common types of storage:
-optical
-magnetic
-solid state
Suitable storage devices and storage media for a given application, and the advantages and disadvantages of these, using characteristics:
-capacity
- speed
-portability
-durability
-reliability
- cost.
MEMORY - LESSON 3
STARTER
KEYWORDS
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Optical Storage - uses lends and a light beam to read and write data onto a disk
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Magnetic Storage- The magnetic storage devices uses magnetised rigid plates that rotate
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Solid-State Storage- Flash memory is very common form of personal portable file storage and is often used as a USB device to transfer data.
INPUT
While computers are able to process data to solve problems, they would certainly not be as useful and in such a widespread use as they are, if every time we needed to process something the programs had to be typed in.
Most of our computers however, require a general- purpose computer able to deal with a range of task. A computer system needs secondary storage to store data long-term. RAM is volatile memory, so its contents are lost when the the computer is turned off.
Secondary storage is needed to store the content of RAM for when they are needed again at a late date.
What is a secondary storage?
Secondary storage refers to any storage - either internal or external to a computer- that is not under the direct control of the CPU. An example of internal secondary storage would be the hard disk; an example of external storage (often refereed to as offline storage) would be CD or external hard drive. Data that is directly under the control of the CPU is called primary storage. An example of this would be the RAM.
There are 3 type of secondary storage;
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Optical Storage
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Magnetic Storage
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Solid-State Storage
1. Optical Storage
Optical storage uses lens and a light beam to read and write data onto a disc. Example of optical storage discs are supplied in two basic forms: read only and read/write.
Read only Media (CD-ROM, DVD-ROM) are written to once st the manufacturing stage and are used to distribute programs, videos or data that is read only.
The read/write variety (CD-RW and DVD-RW) can be used as secondary storage to back up data.
The transfer of times for data are quite slow compared to other portable media but the low cost and robust nature of these makes them ideal for transferring large files.
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CD- can hold around 700 MB of data
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DVD can hold around 4.7 GB.
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Blue-ray can hold up to 25 GB per layer and
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it is available in dual layer 50 GB, triple layer
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100 GB and quad layer 128 GB.
Advantages and disadvantages of Optical storage include
2. Magnetic storage
The magnetic storage devices uses magnetised rigid plates that rotate. Modern internal magnetic drive size are now typically measured in terabytes (1 million megabytes). A 6 TB hard disk drive can be bought today for under £200. The magnetic disk drive is reliable and cost-effective storage solution, provide high capacity at low cost. Now it is used in most personal desktop and laptop computers as well as large commercial systems.
The magnetic disk drive (or hard drive) will store the computer's operating system (s), installed applications or programs and users' data.
3. Solid sate storage
An SSD (solid-state drive or solid-state disk) is a nonvolatile storage device that stores persistent data on solid-state flash memory. Solid-state drives actually aren't hard drives in the traditional sense of the term, as there are no moving parts involved.
Solid- state storage uses flash memories to store data.
Flash memory is very common form of personal portable file storage and is often used as a USB device to transfer data. Many computers use large solid-state- drives(SSD) as an alternative to magnetic disk drives.Very large solid-drive (SSD) are increasingly available for a large-scale data storage. SDD is relatively expensive and use interconnected flash memory chip that can permanently be installed into different devices.
SDD are expensive compared to magnetic disk drive, and currently all devices for home computers do not have the same capacity as a magnetic disk drive. For example, you can buy magnetic hard disk for just under £200 with 6 TB capacity, you can also buy with the same amount of money a 512 GB of SSD storage.
Capacity
The choice of media is often determined by the number and type of files to be stored there are a number of element that we may want to consider when choosing a suitable storage device for our data, these are :
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Capacity - the amount of data we can store on the device
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Speed- the speed at which we can transfer data
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Portability- whether we need to move the data around and carry it with us
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Durability- the length of time the device will safely store data without failing.
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Reliability - whether data is stored without any technical error, and data is still reliable.
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Cost - the cost of manufacture for a device
When we store a file it takes up a certain amount of storage space. We call this the file size, and we call the amount of data a storage device can store its storage capacity. We may want to calculate the size of the file to see how big it will be to store. Most computers will do this for us but it is useful for us to know how to do this as well.
To calculate the size of a file we need to know how data is measured. To measure data, we can use the following units:
Example
Charlie has an image that is 16-bit. It has a resolution of 100 pixels by 10 pixels. Charlie wants to calculate the size of the image file and he wants to write this in kB.
This is how Charlie can calculate the size of the file:
100 x 10= 1000 This means there are 1000 pixels in the image.
100 x 16=16 000 Each pixel in the image requires 16 bits of storage.
This means the size of the file 16,000 bits. Charlie wants to write this in KB.
16 000/8=2000 This calculation will give Charlie the file size in bytes.
2000/1024=1.96 This calculation will give Charlie the file size in KB.
EXAM TIP
People often interchange “memory” with “storage,” and vice-versa.
taSK 1
Following from the starter, In groups of 4, you need to identify as many information as you can about the your device.
You can use the internet or text book. You have 10 Min
Then swap with the other group what they can add to your device.
taSK 2
Vicky has been on holiday and has taken lots of photos. The memory in her camera is now full and she needs to transfer her photos to an external secondary storage device.
1) What is the difference between primary storage and secondary storage?(1)
2) Identify the three common storage technologies Vicky can choose from. (3)
3) State four characteristics of secondary storage devices that Vicky should consider when choosing a device.(4)
TASK 3
1) Which storage device is most suitable for the following tasks.
2) Draw a diagram to summarise cost, speed and capacity for different types of secondary storage.
did you know?
The optical disk, CD was invented in the mid -1980's and the DVD in the late 1990's.
EXAM TIP
People often interchange “memory” with “storage,” and vice-versa.
did you know?
The first magnetic disk drive was first invented by IBM in 1956. it had a stack of 50 platters, was the size of fridge, was able to store around 5 MB of data and cost $50 000.
did you know?
In the starter sheet, Choose one of the Secondary device and write as many facts you know about it.
The swap with the person next to you and see how many other facts can they add.
Click on the Home learning button to download your home learning document.
Due in Next lesson
The need for secondary storage
• data capacity and calculation of data capacity requirements common types of storage:
-optical
-magnetic
-solid state
Suitable storage devices and storage media for a given application, and the advantages and disadvantages of these, using characteristics:
-capacity
- speed
-portability
-durability
-reliability
- cost.
The need for secondary storage
• data capacity and calculation of data capacity requirements common types of storage:
-optical
-magnetic
-solid state
Suitable storage devices and storage media for a given application, and the advantages and disadvantages of these, using characteristics:
-capacity
- speed
-portability
-durability
-reliability
- cost.