Understanding Sparse Files and LRU Cache Management in File Systems

Many file systems allow you to create a logical file with 'empty' (fully zeroed) blocks that are not physically backed until they get written to.

The file system is maintaining metadata on which blocks of the file are physically represented on disk and which are not.

An LRU cache for sparse file blocks would track which blocks have been recently accessed and evict the least recently used ones when space is needed.

This approach can significantly reduce disk space usage for files that are mostly empty but have occasional writes scattered throughout their logical range.

The implementation would need to balance the overhead of maintaining the LRU metadata against the benefits of reduced physical storage usage.