1. 3 - STORAGE: DATA CAPACITY CALCULATIONS

2. Thought for the day - Storage
The Met Office (weather forecasting) computer has 17 petabytes of data storage = 17,000 terabytes. It also has 48,000 CPU cores and weighs 140 tonnes!

3. Big Picture - Storage In this topic, you need to understand:
the need for secondary storage
common types of storage: optical, magnetic, solid state and their characteristics - capacity, speed, portability, durability, reliability, cost
the advantages and disadvantages of these storage methods
suitable storage devices and storage media for a given application based on their characteristics
data capacity and calculation of data capacity requirements

4. Learning Objectives By the end of today’s lesson, you will be able to:
Estimate storage requirements and the most appropriate storage media/device
Estimate data capacity requirements for different file types

5. Starter - Data capacity
Put them in order from lowest to highest: GB KB
Byte MB
Nibble
Bit
Which storage device/media might have the following capacities:
700MB
Up to 185 TB
4.7 GB
128GB – 4TB
1.44MB
Storage media have a capacity measured in bytes. The three common measures are:-
Megabyte (MB) - a million bytes (well, a 1,024,000 bytes to be precise)
Gigabyte (GB) - thousand Megabytes
Terabyte (TB) - thousand Gigabytes
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

6. Starter - Data capacity
Put them in order from lowest to highest:
Bit
Nibble
Byte KB MB GB
Which storage device/media might have the following capacities:
700MB = CD
Up to 185 TB = Mag Tape
4.7 GB = DVD
128GB – 4TB = SSD
1.44MB = Floppy Disk
Storage media have a capacity measured in bytes. The three common measures are:-
Megabyte (MB) - a million bytes (well, a 1,024,000 bytes to be precise)
Gigabyte (GB) - thousand Megabytes
Terabyte (TB) - thousand Gigabytes
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

7. Convert …… 64 Bits > Bytes 2000KB>MB 5GB > MB 64MB > GB
1000TB>GB
Size
Equal to
8 bits
1 byte
1024 bytes
1000 bytes
1 kilobyte
1024 kilobytes
1000 kilobytes
1 megabyte
1024 megabytes
1000 megabytes
1 gigabyte
1024 gigabytes
1000 gigabytes
1 terabyte gb
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

8. Converted …… 64 Bits = 8 Bytes 2000KB = 2MB 5GB > 5000MB
1000TB = GB
Size
Equal to
8 bits
1 byte
1024 bytes
1000 bytes
1 kilobyte
1024 kilobytes
1000 kilobytes
1 megabyte
1024 megabytes
1000 megabytes
1 gigabyte
1024 gigabytes
1000 gigabytes
1 terabyte gb
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

9. Data capacity To be absolutely precise, we should say that
1 KB = 1,024 bytes
In exams, we can use 1KB = 1,000 bytes
This makes the maths easier! But why is that we do you think this is?
Think about binary which is base 2 because it can only use 1 or Could 1000 be represented as 2 to the power of anything?
You will be expected to be able to calculate file sizes and storage space needs – we’re going to look at both today
You need your Maths head on!
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

10. Calculating storage - 1
In your exam you might be given a scenario and asked to work out how much data storage would be needed.
Example 1 - music storage on a smart phone
You have a smart phone with 6GB of storage.
You want to store music on the phone.
A typical mp3 encoded music file takes up 4MB.
How many tracks can be stored on the phone?
Hint – convert capacity to the same size of storage
units as the photos before you start!
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

11. Calculating storage - 1
In your exam you might be given a scenario and asked to work out how much data storage would be needed.
Example 1 - music storage on a smart phone
You have a smart phone with 6GB of storage.
You want to store music on the phone.
A typical mp3 encoded music file takes up 4MB.
How many tracks can be stored on the phone?
Answer: Convert GB into MB so you are using a common quantity. 6GB = 6000MB
6000 MB/4 MB = 1,500 music files
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

12. Calculating storage - 2
In your exam you might be given a scenario and asked to work out how much data storage would be needed.  
Example 2 - photo storage on a smart phone
You have a smart phone with 6GB of storage.
You want to store photos on the phone.
Assume that a typical photo taken by a phone will be around 2MB
Hint – convert capacity to the same size of storage
units as the photos before you start!
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

13. Calculating storage - 2
In your exam you might be given a scenario and asked to work out how much data storage would be needed.  
Example 2 - photo storage on a smart phone
Assume that a typical photo taken by a phone
will be around 2MB
Answer: Convert GB into MB so you are using the same quantity. 6GB = 6000MB
6000 MB / 2 MB = 3,000 photos
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

14. Calculating storage - 3
In your exam you might be given a scenario and asked to work out how much data storage would be needed.  
Example 3: Storage in the cloud
On your PC, you currently have 2500 documents with an average file size of 50KB
You also have 5 movies using 2GB of space each.
You also have 1500 photos with an average file size of 3MB
If you wanted to store all of these things in the cloud, how much storage space would you need to purchase per month?
Hint – convert all files to the same size of storage units
before you start!
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

15. Calculating storage - 3 Example 3: Storage in the cloud
2500 documents with an average file size of 50KB
5 movies using 2GB of space each.
1500 photos with an average file size of 3MB
If you wanted to store all of these things in the cloud, how much storage space would you need to purchase per month?
Answer
Because the storage of each file needs to be added up, you should keep to the same size of storage units. So for this example we will use megabytes.
Text files: 50KB is 0.05MB, so storage of text files is 2500 x 0.05MB = 125 MB
Video files: 2 gigabytes is 2000 megabytes so they take 5 x 2000MB = 10,000 MB
Photo files: 1500 x 3MB = 4,500 MB
Adding them all up = = MB
Convert the MB back into GB: MB = GB.
So you would need to purchase at least 15GB of storage space.
You would then need to research the most cost effective way of acquiring this cloud storage
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

16. Calculating file sizes
You will also be expected to be able to calculate file sizes
Different types of files obviously store different types of data – for example, a text file stores characters as binary in ASCII code, an image file stores pixel data stored as binary.
As well as the data we have to allow for “overheads” – this is the metadata about a file which also takes up storage

17. Size of Text files
1 byte per character, + 10% for any overheads (e.g. file type) so 1.1 bytes per character
A text file with 1000 characters will be approximately what size?
1000 characters * 1.1 bytes =
1100 bytes in total
How many KB?
1100/1000 = 1.1 KB
1100/1024 = 1.07KB
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

18. Images
Pixel = the smallest element of a picture, the tiny “square” of colour
An image is 1024 x 720 pixels. It has 256 different colours.
256 colours = 8 bits per pixel (1 byte), because with 8 bits you can have 256 different colours (28)
File size =(Number of pixels * number of bytes per pixel) + 10% for overheads
Number of pixels = 1024 * 720 = pixels
So what’s the file size of the image?
* 1.1 = bytes
811008/1000 = 811KB
811008/1024 = 792KB
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

19. Database A database record has 4 fields:
Data Type
No. Bytes
Text
1 byte per character
Integer
4/8 bytes
Real
Boolean
1 byte
Date
8 bytes
A database record has 4 fields:
FirstName (text up to 10 characters)
Surname (text up to 10 characters)
DateOfBirth
NumberOfChildren
The database will need to store 100 records.
Step 1: How many bytes in 1 record.
FirstName = 10 bytes, Surname = 10 bytes, DateOfBirth = 8 bytes, NumberOfChildren = 4 bytes.
Total = 32 bytes
Step 2: Multiply by the number of records: 32 * 100 = 3200 bytes
Step 3: Add 10% for overheads – 10% of 3200 = 320, = 3520KB
OR 3200 * 1.1 = 3520 bytes or 3.52 KB
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

20. Size of Sound Files 1200/1000 = 1.2 KB 1200/1024 = 1.17 KB
bytesPerSample * samplesPerSecond * channels * duration
A sound file has 2 bytes per sample, it takes 10 samples per second, over 2 channels and is 30 seconds long.
Approximately what size will it be?
2 * 10 * 2 * 30 = 1200 bytes
How many KB?
1200/1000 = 1.2 KB
1200/1024 = 1.17 KB
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

21. How to show your understanding
Without using a calculator:
Estimate the file size of each file described on the worksheet.
Make sure you show your workings!
Extension: repeat the calculations based on 1KB =1024B
Extension Plus: write 4 exam questions, one for each type of file which we can use to test each other
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

22. Answers Basic data Answer 1000B 1024B 1 10000 * 1 * 1.1 =11000 bytes
11KB
10.7KB 2
( ) * 200 * 1.1
= 57 * 200 * 1.1
=12540 bytes
12.24KB 3
2030 * 1000 * 2 * 1.1 =
4466KB
4361.3KB
4.3GB 4
4 * 100 * 1 * (2 * )
=400 * (150)
=60000
60KB
58.6KB
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

23. Plenary
Working in mixed pairs, in your books, put these files into order from smallest to largest:
A text file with 220 words
An image that is 1000 x 200 pixels, with 1 byte per pixel
A sound file that has 1 byte per sample, it takes 2 samples per second, over 1 channel and is 600 seconds long
An image that is 100 x 200 pixels, with 2 bytes per pixel
A text file with 3000 words
Can you explain: What does 'data compression' mean?
Why is data often 'compressed' before it is stored?
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

24. Plenary Answer A text file with 220 words (220*1.1 = 242 bytes)
A sound file that has 1 byte per sample, it takes 2 samples per second, over 1 channel and is 600 seconds long (1*2*1*600 = 1200 bytes)
A text file with words (30000 * 1.1 = bytes)
An image that is 100 x 200 pixels, with 2 bytes per pixel (100*200*2*1.1 = bytes)
An image that is 1000 x 200 pixels, with 1 byte per pixel (1000*200*1*1.1) = bytes
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types

25.
Today’s objectives:
Estimate storage requirements &most appropriate storage
Estimate data capacity requirements for different file types