Notes / University Notes / Operating System / Chapter 12: Mass Storage System

Chapter 12: Mass Storage System

Created: 2025-12-16Updated: 2025-12-16

The disk as the OS sees it, where the seek dominates every access, and the scheduling algorithms and RAID arrangements built around that fact.

Disk Structure

disk drives are addressed as large 1-dim arrays of logical blocks
platter -- track -- sector
logical block (sector) mapped onto disk sequentially
- Sector 0: Platter 0, Track 0, Sector 0
- go from outermost track to innermost track
Sector Per Track
- CLV (Constant Linear Velocity)
  - density of bits per track is uniform, keep same data rate
  - rotational speed varies; the inner, the faster
- CAV (Constant Angular Velocity)
  - rotational speed is constant
  - density varies; the inner, the higher