Ontological Layer: The Preservation of State
File Systems & Disks
How the Machine Remembers
The Architecture of Memory
When the power is cut, RAM forgets everything. To achieve true persistence, the OS must map logical, human-readable "Files" onto the raw, mechanical sectors of a hard drive or the erase-blocks of an SSD. Realm 14 documents this massive abstraction: how directories form a namespace, how inodes track scattered data blocks across spinning platters, and how disk-scheduling algorithms optimize the physical travel of the read/write head to minimize mechanical latency.
The 12 Storage Chambers
Ontological Mapping: From Directories to Platters
Persistent Storage
- Information survives power-off
- Difference from volatile RAM
- Files as persistent logical units
- Attributes: Name, Type, Size, Owner
Operations & Access
- Create, Read, Write, Seek, Delete
- Sequential Access (Streams)
- Random / Direct Access (Jumps)
- Indexed Access via key structures
Directories & Links
- Namespace mapping (Name → Metadata)
- Tree-structured hierarchies
- Absolute vs Relative Paths
- Hard Links vs Symbolic Links
Filesystem Metadata
- Information about the files
- File Control Block (FCB)
- Inodes: File identity & data pointers
- Permissions, Owners, Timestamps
Allocation Strategies
- Contiguous: Fast, but fragmentation issues
- Linked: Easy growth, poor random access
- Indexed: Direct access via index block
- External vs Internal Fragmentation
Free-Space Management
- Tracking available storage blocks
- Bitmaps (1 bit per block)
- Linked Free Lists
- Grouping and Counting techniques
HDD Structure
- Platters, Tracks, Sectors, Cylinders
- Seek Time (Head movement)
- Rotational Latency (Waiting for sector)
- Transfer Time (Reading data)
Disk Scheduling
- FCFS (First-Come, First-Served)
- SSTF (Shortest Seek Time First)
- SCAN (Elevator Algorithm)
- C-SCAN, LOOK, C-LOOK variations
SSD & Flash Memory
- No mechanical parts or seek time
- Flash Translation Layer (FTL)
- Wear Leveling & Garbage Collection
- Erase-block constraints
Journaling & Safety
- Crash consistency problems
- Journal: Recording intent before writing
- Metadata vs Data journaling
- Filesystem Consistency Checking (fsck)
RAID & Redundancy
- RAID 0: Striping (Performance only)
- RAID 1: Mirroring (Redundancy)
- RAID 5: Striping + Distributed Parity
- Partitions, Volumes, and Formatting
14 — The Disk Geometry Laboratory
Filesystems transform an undifferentiated collection of spinning magnetic blocks into a structured, named, and protected world of persistent data. With Realm 14 completed, we have traversed the entire horizontal architecture of the computer. The final step is Realm 15: The Computer Laboratory, where all these systems combine.