File system
A file system is a set of rules that manage the way files are stored and retrieved on a disk. It defines how data is written to disk.
Cluster - Allocation unit
This is the smallest allocation unit imposed by the file system. It is made up of multiple sectors (the smallest physical part: ~512 bytes). The cluster is the smallest space a file can occupy on a disk.
For example: if the cluster size is 4 Kb, to store a 10 Kb file, 3 clusters are needed (for a total of 12 Kb). The remaining 2 Kb is lost. The space lost is included in the file size.
External disk
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FAT32
- Compatible with all major operating systems
- Maximum file size is 4 GB
- Minimum allocation size is 512 bytes
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ExFAT (enhanced FAT32)
- No file size limit
- Minimum file size for allocation is 4 Kb
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NTFS
- Proprietary file system developed by Windows
- Free drivers available for Linux
- No file size limit
- Minimum allocation size is 512 bytes (for small volumes)