💽 Disk Scheduling Simulator & OS Storage Architecture Lab

A Next-Generation Interactive Operating Systems Simulator & Hardware Physics Suite

⚡ Live Demo • 📖 Documentation • 🧠 Algorithms • ⏱️ Hardware Physics • 👨‍💻 Developed By

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🌌 Overview

The Disk Scheduling Simulator & OS Storage Architecture Lab is an interactive, browser-based computer science laboratory designed to visualize, benchmark, and teach Operating System Storage Subsystems.

Bridging the gap between classical theoretical algorithms and real-world storage hardware, it simulates both Mechanical Magnetic Hard Disk Drives (HDDs) (with rotating platters and actuator arm kinematics) and NAND Flash NVMe Solid State Drives (SSDs) (with uniform zero-seek Flash Translation Layer controllers).

  ┌─────────────────────────────────────────────────────────────────────────┐
  │                         SIMULATOR ARCHITECTURE                          │
  ├───────────────────┬───────────────────────────────┬─────────────────────┤
  │ 🎛️ CONFIG & SPECS │     🖥️ MULTI-VIEW ENGINE      │  📊 LIVE TELEMETRY  │
  │ • 11 Schedulers   │  • 🎯 1D Linear Physical Track │  • Total Seek Cyl   │
  │ • Direction Toggle│  • 📈 2D Trajectory Seek Graph│  • Seek Latency ms  │
  │ • Drive RPM (5.4k-│  • 💽 Concentric 2D Platter   │  • Rotational Delay │
  │   15k RPM)        │  • 💽 3D Cylinder Multi-Stack │  • Access Time ms   │
  │ • HDD vs. SSD Mode│  • ⚡ NVMe SSD NAND Die Grid  │  • Head Reversals   │
  │ • Preset Workloads│  • 🐧 Linux Kernel Multi-Queue│  • Live Progress    │
  │ • Live I/O Stream │  • 💻 In-Browser JS Sandbox   │  • Step Math Proof  │
  └───────────────────┴───────────────────────────────┴─────────────────────┘

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🌟 Complete Feature Matrix

🎛️ 1. Eleven Scheduling & Linux Kernel Algorithms

• Classical OS Schedulers:
  • FCFS (First-Come, First-Served)
  • SSTF (Shortest Seek Time First)
  • SCAN (Elevator Algorithm — ↗ High / ↙ Low Directional)
  • C-SCAN (Circular SCAN with rapid return)
  • LOOK (Optimized Elevator reversing at boundary requests)
  • C-LOOK (Circular LOOK)
  • F-SCAN (Dual-Queue Freeze SCAN preventing starvation)
  • N-Step SCAN (Batched SCAN with configurable batch size $N$)
  • User Custom Sequence (Raw input trace verification)
• Modern Linux Kernel Schedulers:
  • Linux Deadline Scheduler: Separate Read FIFO ($500\text{ ms}$) and Write FIFO ($5000\text{ ms}$) expiration queues alongside a sorted sector dispatcher.
  • Linux CFQ (Completely Fair Queuing): Multi-process round-robin time-slicing across concurrent processes (MySQL vs Backup vs Video).
  • Linux NOOP / None: Pure FIFO request merging with zero sorting overhead (the gold standard for NVMe SSDs).

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🖥️ 2. Seven Interactive Multi-Dimensional Visualizers

Mode	Name	Visual Experience & Physical Details
🎯	1D Linear Track	High-DPI physical track with glowing magnetic head pointer (H), color-coded request nodes, seek arcs, and interactive tooltips.
📈	2D Seek Graph	OS textbook-style coordinate chart plotting Time Steps ($Y$-axis, top-to-bottom) vs. Cylinder Number ($X$-axis, left-to-right).
💽	Concentric 2D Platter	Kinetic rotating magnetic platter ($0 \to \text{Max}$) with a mechanical actuator arm pivoting its read/write head tip over tracks.
💽	3D Cylinder Stack	Isometric stack of 3 platters (6 surfaces: Head 0 to Head 5) with a synchronized multi-head actuator comb demonstrating CHS addressing.
⚡	NVMe SSD Flash Array	4-channel, 16-die NAND Flash cell array demonstrating Flash Translation Layer (FTL) wear-leveling and zero mechanical seek penalty.
🐧	Linux Kernel Lab	Real-time multi-queue visualization showing Read FIFO, Write FIFO, and Sorted Dispatcher queues.
💻	In-Browser JS Sandbox	Integrated Monaco-style JavaScript code editor allowing students to write, execute, and test their own custom scheduling algorithms.

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⚡ 3. Storage Hardware Architecture: Mechanical HDD vs. NVMe SSD

Toggle between 💽 Mechanical HDD and ⚡ NVMe SSD with one click:

• Mechanical HDD Mode:
  • Accurately models physical actuator arm acceleration ($2.0\text{ ms startup} + \Delta C \times 0.15\text{ ms/cyl}$) and rotational delays across $5400$, $7200$, $10000$, and $15000\text{ RPM}$ spindles.
• NAND Flash NVMe SSD Mode:
  • Demonstrates why classical elevator schedulers are bypassed on SSDs in favor of NOOP/none, showcasing uniform $\sim 0.04\text{ ms}$ latency across arbitrary logical block addresses.

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📐 4. CHS ↔ LBA Translation Calculator

Built-in live mathematical translator converting between Cylinder-Head-Sector (CHS) and Logical Block Addressing (LBA): $$\text{LBA} = (C \times \text{HeadsPerCyl} + H) \times \text{SectorsPerTrack} + (S - 1)$$

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🎞️ 5. Interactive Drag-to-Scrub Timeline & Voice Narration

• Video-Style Scrubber: Drag continuously through the seek history to inspect head positions at any micro-step.
• AI Voice Narration (V): Live Web Speech API voice synthesis announcing each cylinder seek.
• Binaural Stereo Audio: Web Audio stereo panner that pans sound left-to-right matching the head's physical cylinder position.

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🎓 6. Gamified OS Exam Quiz Arena

• Procedurally generated university exam questions testing next-cylinder predictions.
• Multiple-choice cards, streak tracker (🔥 Streak), score tracking, and mathematical step explanations.

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📄 7. Homework Solution & Data Export Suite

• 📄 Homework Solution (.md): Full formatted Markdown assignment report with LaTeX formulas, seek distance tables, and final metrics ready to submit for university coursework.
• 📊 Telemetry Dataset (.csv): Raw numerical step-by-step dataset.
• 🖼️ Canvas Snapshot (.png): One-click high-resolution diagram export.

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🌓 8. Dual Theme Engine

• Dark Obsidian Glass (Cyberpunk neon glow, default)
• Light Academic Paper (High-contrast, classroom projector friendly)
• Toggle instantly via Header button or T shortcut with localStorage persistence.

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🧠 Supported Scheduling Algorithms Comparison

Algorithm	Type	Time Complexity	Starvation Risk	Directional	Best Use Case
FCFS	Classical	$\mathcal{O}(N)$	None (100% Fair)	No	Light, sequential workloads
SSTF	Classical	$\mathcal{O}(N^2)$	High (Boundary Starvation)	No	Batch workloads with clustered requests
SCAN	Classical	$\mathcal{O}(N \log N)$	None	Yes (↗ / ↙)	High-load shared HDD servers
C-SCAN	Classical	$\mathcal{O}(N \log N)$	None	Yes (↗ / ↙)	Systems requiring uniform wait times
LOOK	Classical	$\mathcal{O}(N \log N)$	None	Yes (↗ / ↙)	General-purpose desktop HDDs
C-LOOK	Classical	$\mathcal{O}(N \log N)$	None	Yes (↗ / ↙)	High-throughput server workloads
F-SCAN	Classical	$\mathcal{O}(N \log N)$	None	Yes (↗ / ↙)	High dynamic arrival environments
N-Step SCAN	Classical	$\mathcal{O}(N \log N)$	None	Yes (↗ / ↙)	Systems prone to arm stickiness
Linux Deadline	Linux Kernel	$\mathcal{O}(N \log N)$	Guaranteed None	Yes	Real-time & database servers (MySQL)
Linux CFQ	Linux Kernel	$\mathcal{O}(P \times N)$	None	Round-Robin	Multi-user & desktop Linux systems
Linux NOOP	Linux Kernel	$\mathcal{O}(N)$	None	No	NVMe SSDs, Flash, & Virtual Disks

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⏱️ Hardware Drive Physics & Latency Equations

Disk access time is calculated using the official Operating Systems physics formulation:

$$\text{Total Access Time } (T_{\text{access}}) = T_{\text{seek}} + T_{\text{rotational}} + T_{\text{transfer}}$$

1. Seek Time ($T_{\text{seek}}$)

The time required for the mechanical actuator arm to position the read/write head over the desired cylinder track: $$T_{\text{seek}} = T_{\text{startup}} + (\Delta C \times \text{Seek Rate})$$

• Default: $2.0\text{ ms startup} + (\text{Seek Cylinders} \times 0.15\text{ ms/cyl})$

2. Average Rotational Latency ($T_{\text{rotational}}$)

The average time for the requested disk sector to rotate under the read/write head (equivalent to half a rotation): $$T_{\text{rotational}} = \frac{1}{2} \times \left(\frac{60}{\text{RPM}}\right) \times 1000\text{ ms}$$

Spindle Speed (RPM)	Category	Average Rotational Delay
5,400 RPM	Laptop / Power-Saving HDD	5.56 ms
7,200 RPM	Desktop Standard HDD	4.17 ms
10,000 RPM	VelociRaptor High-Performance	3.00 ms
15,000 RPM	Enterprise SAS / Server HDD	2.00 ms

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⌨️ Keyboard Shortcuts

Shortcut	Action
Space	Play / Pause animation playback
←	Previous Step (Step backward)
→	Next Step (Step forward)
Home	Jump to Start (Initial head position)
End	Jump to End (Complete simulation)
R	Reset simulation state
T	Toggle Theme (Dark Obsidian ⇄ Light Academic)
V	Toggle AI Voice Narration
Canvas Click	Inject I/O Request at clicked cylinder/sector

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🚀 How to Run Locally

Because the project is built with Pure Vanilla Web Technologies, zero build tools or npm package installations are required.

Method 1: Local HTTP Server (Python)

python -m http.server 8000

Open http://localhost:8000/project.html in your browser.

Method 2: Direct File Open

Double click project.html directly in any modern web browser.

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👨‍💻 Developed & Maintained By

PRIYA RANJAN

Full-Stack Engineer & Systems Architecture Enthusiast

Crafted with ❤️ and precision for Operating Systems education and computer engineering students worldwide.

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📜 License

This project is licensed under the MIT License — see the LICENSE file for full details.

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_{⭐ If you find this project helpful for your Operating Systems studies or coursework, please consider starring the repository!}