You are designing a system to crowdsource student evaluations of college courses. As part of this...

 

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You are designing a system to crowdsource student evaluations of college courses. As part of this system, you want to store a table of reviews containing the following information (for each review): • Review Date - Date (3 bytes) • Academic Year - int32 • Academic Quarter - char[10] • Course ID-char[5] • Rating (0.0 to 5.0) - float32 • Grade in the course - char[2] • Estimated Hours Per Week - int32 • Review (text) - char[224] Question 2.1 What is the size of each row in bytes? Question 2.2 Assume that this data is stored on a HDD in 64MB IO blocks and these blocks are grouped in 2x64MB 10 blocks. How many rows can be stored per 64MB 10 block? Question 2.3 How many 2x64MB blocks would you need to store 2 million rows? Question 2.4 Relevant information: • According to the registrar, this quarter there are 16500 students (undergrad and graduate) enrolled. • Of these, about 1500 are grad students finishing their degree, which will be excluded. • Of the remainder, some are grad students who might be doing research full-time and not taking classes. Let's consider this and approximate that there are exactly 15,000 class-taking students at Stanford. • Let's assume that on average each class-taking student takes 3 classes per semester (including the summer semester). • Let us also assume that writing course evaluations is optional and 50% of students who take a course will write an evaluation. (Note: If a student chooses not to write an evaluation, no row is added to the table.) After 10 years (30 semesters), how large in MB will the table of course reviews be? Round your answer to 1 decimal place. Question 2.5 Q2.5-2.7 follow from 2.4. How many 64MB blocks would be needed to store the table of course reviews? Question 2.6 Now, let's say you would like to read from your table and retrieve a particular evaluation (row). Let's make the following assumptions about the hardware that is used to store the table: • Your data is all stored on HDDs • Use the numbers given in the notes/instructions for all calculations. How long would it take in hours to retrieve an evaluation (row) if the table rows are stored randomly on HDD (we must access and scan every row)? Round your answer to 1 decimal place. Question 2.7 How long would it take in seconds if the rows are grouped in 64MB blocks (which are randomly stored on HDD)? Note: in your calculations, please use a whole number of blocks (round up: e.g. 16.1 blocks → 17 blocks). You are designing a system to crowdsource student evaluations of college courses. As part of this system, you want to store a table of reviews containing the following information (for each review): • Review Date - Date (3 bytes) • Academic Year - int32 • Academic Quarter - char[10] • Course ID-char[5] • Rating (0.0 to 5.0) - float32 • Grade in the course - char[2] • Estimated Hours Per Week - int32 • Review (text) - char[224] Question 2.1 What is the size of each row in bytes? Question 2.2 Assume that this data is stored on a HDD in 64MB IO blocks and these blocks are grouped in 2x64MB 10 blocks. How many rows can be stored per 64MB 10 block? Question 2.3 How many 2x64MB blocks would you need to store 2 million rows? Question 2.4 Relevant information: • According to the registrar, this quarter there are 16500 students (undergrad and graduate) enrolled. • Of these, about 1500 are grad students finishing their degree, which will be excluded. • Of the remainder, some are grad students who might be doing research full-time and not taking classes. Let's consider this and approximate that there are exactly 15,000 class-taking students at Stanford. • Let's assume that on average each class-taking student takes 3 classes per semester (including the summer semester). • Let us also assume that writing course evaluations is optional and 50% of students who take a course will write an evaluation. (Note: If a student chooses not to write an evaluation, no row is added to the table.) After 10 years (30 semesters), how large in MB will the table of course reviews be? Round your answer to 1 decimal place. Question 2.5 Q2.5-2.7 follow from 2.4. How many 64MB blocks would be needed to store the table of course reviews? Question 2.6 Now, let's say you would like to read from your table and retrieve a particular evaluation (row). Let's make the following assumptions about the hardware that is used to store the table: • Your data is all stored on HDDs • Use the numbers given in the notes/instructions for all calculations. How long would it take in hours to retrieve an evaluation (row) if the table rows are stored randomly on HDD (we must access and scan every row)? Round your answer to 1 decimal place. Question 2.7 How long would it take in seconds if the rows are grouped in 64MB blocks (which are randomly stored on HDD)? Note: in your calculations, please use a whole number of blocks (round up: e.g. 16.1 blocks → 17 blocks).

Answer rating: 100% (QA)

Question 21 Size of each row in bytes Review Date 3 bytes assuming a standard date format Academic Year 4 bytes int32 Academic Quarter 10 bytes char10 Course ID 5 bytes char5 Rating 4 bytes float32 Gr... View the full answer