Chunk Layout

Chunk, Block, and Slice are first-class concepts in BrewFS, making random IO, object layout, compaction, and GC easy to reason about.

• Chunk — a fixed-size region of a file; the unit of metadata mapping.
• Block — the unit stored on the object backend.
• Slice — a contiguous write within a chunk; new writes append new slices.

Random writes never rewrite whole objects: they append slices, which the read path merges by offset (newest slice wins, holes are zero-filled). Background compaction keeps slice counts bounded.