Filesystems and Storage

Why this module exists

Filesystems are about structure and mapping. A path maps to an inode; an inode maps to blocks; blocks map to disk sectors. Correctness requires deterministic addressing and careful handling of indirection.

1) Inodes and block addressing

Inodes use a mix of direct and indirect pointers:

• Direct blocks are stored in the inode.
• Single indirect blocks point to a table of block pointers.
• Double indirect blocks point to a table of tables.

This structure balances small-file efficiency and large-file capacity.

2) Disk scheduling

Disks are slow; seek time dominates. Scheduling algorithms reduce total seek distance:

• FCFS: simple but often worst-case
• SSTF: short-seek-first, can starve
• SCAN/LOOK: sweep in one direction

What you will build

• Inode block mapping with direct and indirect pointers
• Disk scheduler simulation (LOOK)

Key takeaways

• Filesystem correctness is about precise mapping.
• Disk scheduling is a policy tradeoff between fairness and throughput.