EntropyFS

de Beer, R. (2026). EntropyFS: Entropy-Native Configurational Storage as a Filesystem Substrate - Broad Prior-Art Technical Disclosure and Research Architecture (Version v1.0). Zenodo. https://doi.org/10.5281/zenodo.22092869

Persist irreducible state. Materialize structure. Preserve exact bytes. Measure everything.

EntropyFS is a native-Rust, mountable Linux filesystem whose central research premise is:

Logical bytes are an interface presented to applications. They do not have to be the primary persisted representation. EntropyFS persists the minimum exact reversible entropy/configuration state necessary to reproduce those bytes.

The defining equation:

X = Materialize(D)

X is the exact logical byte sequence; D is the persisted representation descriptor. A more general family:

X = T(E(U, S, P)) ⊕ R

U = versioned entropy universe · S = seed/state · P = rank/coordinate · T = bounded reversible transform · R = exact residual · E = deterministic materialization.

EntropyFS does not claim to evade information theory: the SSD still stores physical bits. Its innovation is to make entropy state, mathematical rank/configuration, immutable references, deterministic generators, transforms, and irreducible residuals first-class storage representations instead of assuming logical byte blocks must themselves exist at rest. For random/encrypted/incompressible data it converges gracefully toward ordinary physical storage (RAW fallback) — that is a success condition, not a failure.

Current status

Measured results

All performance and storage-density claims are governed by docs/performance/methodology.md; admitted results live in evidence/performance/ (see evidence/performance/INDEX.md).

FUSE-frontend before/after pair (Phase 6, same workloads, same machine):

The fsync regression is the measured cost of deferred durability and is reported honestly; the before half reproduces the crashes the oversized-descriptor fix (Phase 6) eliminated.

What EntropyFS does and does not claim:

• The synthetic ablation fixture (evidence/ablation-2026-08-25.json) is an ablation fixture, never a headline: on a corpus containing four unique 64 KiB chunks its 16.876× is dominated by content-addressed dedup. The campaign's structured-corpus ratios (up to 989× on that same corpus) are structural/configurational — the d04227f campaign measures the dedup contribution at 0 on that corpus (one group-commit batch: pending index entries are invisible to the dedup lookup, and the uniform zones are already structurally cheap), correcting the earlier “dedup-dominated” labels. Both are presented as ablation data only.
• The campaign's ablation evidence is two tables, both kept forever: the strict cumulative ladder A0–A8 (each step adds one mechanism) and the leave-one-out table (one mechanism disabled at a time). The first campaign's nine-row table is the leave-one-out table; it predates the two-table rule and is amended as such in evidence/performance/INDEX.md (protocol note, never rewritten).
• The campaign's DSFB investigation (5+5 repeated runs) found: with DSFB ranking enabled vs disabled, the final physical representation is byte-identical (79,298 B) while write throughput is 765 vs 335 MiB/s and user CPU halves — evidence for DSFB's assigned role as candidate-search budget intelligence, not compression. Single synthetic corpus; under further study.
• The campaign's H2 experiment (synthetic drift corpus) is now a sealed three-campaign controlled series: 67d977a +7.2% (RANS-era floor), a6641d1 −24% (SequenceRans floor, positional residuals only), 43bf17e +35.2% (SequenceRans floor + BASE_SEQUENCE shift-aware deltas — sequential 2.752× vs shuffled 1.784×). The shuffled control grows in the delta campaign because copy/literal deltas also exploit structural similarity between unrelated-history chunks — the control no longer isolates pure temporal causality, and that confounding is itself recorded as the finding.
• Random/encrypted/already-compressed data falls back toward RAW (urandom 0.997×, zstd -19 pack 0.993×) — the honest negative control.

Honesty rules

• A 128-bit seed does not "store" a gigabyte. Descriptor bits select at most 2^k states; every persisted bit is accounted (docs/theory/information-accounting.md).
• No hidden corpus, no network, no RNG in materialization, no CPU-dependent floating point. The universe specification is part of the format version.
• No arbitrary generator programs: the descriptor language is bounded and not Turing-complete (docs/adr/0005-representation-set.md).
• DSFB has zero decoding authority (docs/adr/0004-dsfb-observer.md).
• statfs reports physical capacity; effective ratio is an observation, never a promise (docs/adr/0018-statfs.md).
• Every optimization claim requires reproducible evidence (docs/performance/methodology.md).

Building

rustup toolchain install stable --profile minimal --component rustfmt,clippy
cargo build --release
cargo test
cargo clippy --all-targets -- -D warnings
cargo fmt --check

Target platform

CachyOS/Arch Linux, x86-64, FUSE (/dev/fuse + fusermount3; kernel CONFIG_FUSE_FS=y). No custom kernel, no out-of-tree module, no reboot.

Reading order

• docs/architecture/overview.md — architecture map
• docs/theory/entropy-medium.md — the information-theory boundary statement
• docs/format/ondisk-v1.md — the on-disk format
• docs/recovery/crash-consistency.md — the crash protocol
• docs/adr/ — all architecture decision records

License

MIT OR Apache-2.0, at your option.