Basics of Magnetic Disk Architecture

Duration: 7 min

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Inside: a video lesson and guided study material.

Module outline

  1. Communication Round: Vocabulary, Subject Verb Agreement (Verb Noun Agreement), Tenses, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Direct and Indirect Speech, Active Passive Voice (Voice), Verbal Analogy (Word Based Analogy), Articles, Preposition, Conjunction, Sentence Construction, English Writing Ability, Communication Assessment
  2. Quantitative Aptitude: Ratio and Proportion (Ratios), Divisibility Rules, Data Interpretation, Mixture and Alligation, Permutation and Combination, Logarithm, Number System, HCF LCM, Speed Time and Distance, Percentage, Average, Powers and Exponents (Surds and Indices), Time and Work, Mensuration and Geometry, Age Problems, Pipe and Cistern, Probability, Profit and Loss, Simple Interest and Compound Interest, Algebra
  3. Analytical and Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Directions (Direction Test), Ranking, Order and Sequence, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Logical Sequence Of Words, Puzzle Solving (Puzzles), Syllogisms, Seating Arrangements, Calendar, Clock, Blood Relations, Cubes & Dices, Venn Diagram, Analytical Reasoning (Counting Figures Reasoning)
  4. Cognizant Gaming Aptitude: Gamified / Game Based Aptitude
  5. Java (Cluster 1): Java
  6. ANSI SQL MySQL (Cluster 1,2,3): SQL
  7. HTML, CSS, JavaScript (Cluster 1,3): HTML, CSS, JavaScript
  8. Python (Cluster 2): Python for Placements by Yash Sir
  9. Cloud Fundamentals (Cluster 2): Emerging Tech Trends
  10. C# (Cluster 3): C#
  11. OOPs: Object Oriented Programming (OOPS)
  12. Technical Assessment (Coding): Coding Questions by Yash Sir, C Programming by Yash Sir, Programming in C++, Pseudo Codes
  13. Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  14. DBMS: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Data Warehousing & Mining, Big Data Systems, NoSQL
  15. Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
  16. Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security, Mobile Technology, Cloud Computing and IoT, Cyber and Info Security
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture covers the physical organization of hard disk drives and the operating system's role in managing disk I/O. The instructor begins by dissecting a diagram of a disk drive, identifying components like the spindle, platter, and read-write head. He then uses a real photo to visualize tracks and sectors. Finally, he introduces disk scheduling, defining disk bandwidth and explaining how the OS queues requests to improve efficiency.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor begins by analyzing a schematic diagram of a hard disk drive displayed on the screen. He points to specific components labeled on the diagram, including the "spindle" at the center, the "platter" which rotates, and the "arm" holding the "read-write head". He explains that data is organized into "tracks" (concentric circles) and "sectors" (pie slices). He physically draws red lines on the top platter to illustrate these tracks and sectors, emphasizing the physical layout. He also points out the concept of a "cylinder," which aligns tracks vertically across multiple platters, labeled as "cylinder c" on the screen.

  2. 2:00 – 5:00 02:00-05:00

    The visual aid switches from a diagram to a photograph of an actual hard disk drive. The instructor uses a digital pen to draw directly on the photo, reinforcing the abstract concepts with physical reality. He draws concentric circles to represent tracks and radial lines to represent sectors, similar to the previous diagram. He writes "S1" to mark a specific sector and "RL" near the head, likely indicating a read/write location. This section bridges the gap between theoretical diagrams and the physical hardware students might encounter, showing how the logical structure maps to the physical device.

  3. 5:00 – 7:30 05:00-07:30

    The lecture transitions to a text-heavy slide titled "Disk scheduling". The instructor explains that the operating system must use hardware efficiently, defining "disk bandwidth" as the total bytes transferred divided by the total time. He details the information contained in a disk I/O request, listing bullet points such as "Whether this operation is input or output," "What is the disk address," "What is the memory address," and "What is the number of sectors." He explains that if the drive is busy, requests are placed in a queue, and the OS uses scheduling algorithms to decide the service order to improve access time and bandwidth. He emphasizes that managing the order of requests is key to efficiency.

The video provides a comprehensive introduction to disk storage and management. It starts by establishing the physical geometry of the disk (platters, tracks, sectors, cylinders) using both diagrams and real photos. It then moves to the logical layer, explaining how the OS handles I/O requests. The core takeaway is that disk scheduling is crucial for optimizing performance by managing the order of requests in a queue to maximize bandwidth and minimize access time.

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