Overview

This chapter focuses on the mass storage structure as part of operating systems, including concepts, device types, disk scheduling algorithms, disk management, and RAID techniques. The material is based on the textbook Operating Systems Concepts.

Storage Management

• Main Memory:
  • Volatile and limited in size.
  • Cannot store all data and programs permanently.
• Secondary Storage:
  • Provides permanent storage for data and programs.
  • Used to create a uniform logical view of stored information.
• File System:
  • Mechanism for data storage and access on secondary storage devices (e.g., HDDs).

Storage Devices

Magnetic Disks (HDDs):

• Provide the bulk of secondary storage in modern computers.
• Characteristics:
  • Tracks: Concentric rings on the disk surface.
  • Sectors: Subdivisions of tracks; the smallest physical storage unit.
  • Cylinders: Set of tracks at the same arm position across platters.

Solid State Disks (SSDs):

• Non-volatile, faster, and more reliable than HDDs.
• Advantages:
  • No moving parts → No seek time or rotational latency.
  • Efficient and fast.
• Disadvantages:
  • More expensive.
  • Lower storage capacity compared to HDDs.

Magnetic Tapes:

• Primarily used for backups and storing infrequently accessed data.
• Characteristics:
  • High storage capacity.
  • Extremely slow access time (~1000 times slower than HDDs).