3 - STORAGE: DATA CAPACITY CALCULATIONS

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!

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

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

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 http://teach-ict.com/2016/GCSE_Computing/AQA_8520/3_4_computer_systems/344_systems_architecture/secondary_storage/miniweb/pg6.htm Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

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 http://teach-ict.com/2016/GCSE_Computing/AQA_8520/3_4_computer_systems/344_systems_architecture/secondary_storage/miniweb/pg6.htm Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

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 1000000gb Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

Converted …… 64 Bits = 8 Bytes 2000KB = 2MB 5GB > 5000MB 1000TB =1000000GB 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 1000000gb Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

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

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

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

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

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

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

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 = 125 + 10000 + 4500 = 14625 MB Convert the MB back into GB: 14625 MB = 14.625 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

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

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

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 = 737280 pixels So what’s the file size of the image? 737280 * 1.1 = 811008 bytes 811008/1000 = 811KB 811008/1024 = 792KB Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

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, 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

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

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

Answers Basic data Answer 1000B 1024B 1 10000 * 1 * 1.1 =11000 bytes 11KB 10.7KB 2 (6+20+15+8+4+4) * 200 * 1.1 = 57 * 200 * 1.1 =12540 bytes 12.24KB 3 2030 * 1000 * 2 * 1.1 = 4466000 4466KB 4361.3KB 4.3GB 4 4 * 100 * 1 * (2 * 60 + 30) =400 * (150) =60000 60KB 58.6KB Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

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

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 30000 words (30000 * 1.1 = 33000 bytes) An image that is 100 x 200 pixels, with 2 bytes per pixel (100*200*2*1.1 = 44000 bytes) An image that is 1000 x 200 pixels, with 1 byte per pixel (1000*200*1*1.1) = 220000 bytes Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types

http://theteacher.info/index.php/storage/self-marking-tests Today’s objectives: Estimate storage requirements &most appropriate storage Estimate data capacity requirements for different file types