What is filesystem?

A filesystem is the method a computer uses to organize, store, and retrieve data on a storage device (like a hard drive, SSD, or USB stick). Think of it as a digital filing cabinet where files are placed in folders, and the system keeps track of where each piece of data lives so you can open, edit, or delete it later.

Let's break it down

  • Storage device: The physical hardware (disk, flash memory) that holds the data.
  • Blocks/sectors: Small pieces of the device where bits of a file are actually written.
  • Files: Individual pieces of data (documents, pictures, programs).
  • Folders (directories): Containers that group related files together.
  • Metadata: Information about each file (name, size, timestamps, permissions) that the filesystem stores.
  • File allocation table / inode table: Internal tables that map file names to the blocks where their data lives.

Why does it matter?

Without a filesystem, a storage device would just be a long string of raw bytes with no way to know where one file ends and another begins. The filesystem makes it possible for you and applications to:

  • Find and open specific files quickly.
  • Keep data organized in a logical hierarchy.
  • Protect files with permissions and access controls.
  • Recover from errors or crashes by tracking where data is stored.

Where is it used?

Every computer, smartphone, tablet, and many embedded devices use a filesystem. Common examples include:

  • Windows computers (NTFS, FAT32, exFAT).
  • macOS and iOS devices (APFS, HFS+).
  • Linux systems (ext4, Btrfs, XFS).
  • External drives, USB sticks, SD cards, and cloud storage services that emulate a filesystem.

Good things about it

  • Organization: Makes it easy to sort, search, and manage files.
  • Reliability: Modern filesystems include error checking, journaling, and recovery features.
  • Security: Supports permissions, encryption, and access control lists.
  • Scalability: Can handle tiny files and massive storage volumes alike.
  • Performance: Features like caching and block allocation improve read/write speed.

Not-so-good things

  • Complexity: Advanced features (journaling, snapshots) can make the system harder to understand and troubleshoot.
  • Fragmentation: Some filesystems can become fragmented over time, slowing performance.
  • Compatibility issues: Not all devices support every filesystem type, leading to read/write limitations.
  • Overhead: Metadata and management structures consume some storage space and processing power.
  • Data loss risk: Corruption of the filesystem’s core tables can make many files inaccessible until repaired.