COMP 3150Operating Systems

Module 4 of 5

Storage and I/O Systems

How persistent data and physical devices are organised. From directory trees, inodes, and journaling to I/O hardware, interrupts, DMA, device drivers, disk scheduling, RAID, and the architecture of solid-state drives.

Open Unit 10 See the units
2 units · 14 lessons Labs 9–10 CLO5 · CLO6 ≈ 3 weeks at recommended pace
File path to inode to disk blocks A directory tree resolves a file name to an inode number, which in turn points to data blocks on disk. DIRECTORY / (root) etc home alice notes.txt usr path → name resolution inode 42 size 4 096 B owner alice mode rw-r--r-- links 1 blocks 3 direct[0] → 7 direct[1] → 12 DISK BLOCKS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 data blocks referenced by inode JOURNAL
2UnitsFiles · I/O
14Lessons7 + 7
2LaboratoriesLabs 9–10
2CLOsCLO5 · CLO6
≈3WeeksAt recommended pace

Module overview

Persistent data and physical devices

Memory is volatile; data that must survive a reboot lives in a file system on a storage device. This module examines both halves of that statement: the abstractions the OS presents for persistent data, and the hardware and software machinery that moves bytes between the CPU and the device.

Unit 10 covers files, directories, metadata, inodes, allocation strategies, journaling, and modern file systems. Unit 11 covers I/O hardware, interrupts, DMA, drivers, disk scheduling, RAID, and solid- state drives. By the end you will be able to reason about file-system performance and reliability, and about the I/O path from a user-level read() to the platter or flash cell.

Module learning outcomes

What you will be able to do

After Module 4 you will be able to

  • Explain file and directory abstractions, metadata, and access methods.
  • Describe inode structure and the mapping from file names to data blocks.
  • Compare allocation strategies and explain journaling and crash consistency.
  • Describe the I/O path: hardware, interrupts, DMA, and device drivers.
  • Analyse disk-scheduling algorithms (FCFS, SSTF, SCAN, C-SCAN, LOOK).
  • Compare RAID levels and explain SSD architecture and wear levelling.
  • Implement and measure a file-system simulator.

Course outcomes addressed

  • CLO5 — Explain file systems, storage systems, and I/O management.
  • CLO6 — Apply Linux systems-programming techniques and operating-system tools.

Units

Units in this module

Laboratory & assessment

How Module 4 is assessed

Laboratories

LabTopicUnit
Lab 9File SystemsUnit 10
Lab 10Storage SystemsUnit 11

Lab 9 includes an inode-tracing exercise and a simple journaling simulation; Lab 10 covers disk scheduling and RAID configuration.

Quizzes, discussion, and Assignment 2

  • Unit 10 quiz — files, inodes, allocation, journaling.
  • Unit 11 quiz — I/O, interrupts, DMA, scheduling, RAID, SSDs.
  • Two discussion activities.
  • Assignment 2 — the File-System Simulator option draws directly on this module. Covers CLO3, CLO4, CLO5, CLO6, and CLO8.

Connected to Assignment 2

If you choose the File-System Simulator for Assignment 2, complete Lab 9 first — it supplies the reference model the assignment extends.

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