# Storage discovery — 2026-09-09

The measured sealed-file listing totals **1,831,276,429,146 bytes (1.83 TB)**
across **6,959 files**. This is the sum of file lengths, not allocated filesystem
blocks, total host disk use, database size, or a measure of reclaimable space.
The concurrent public `stream_archive_sealed_bytes` gauge matched this total.

## What the format establishes

Source: Stream `src/internal/storage/segment.zig`, `segment_writer.zig`, and
`segment_footer.zig`, with `docs/jss-format-v1.md` as a readable format guide.
The guide warns of older upstream commit pins; the current writer establishes
that `compressed_size` excludes the 8-byte frame length prefix.

- The listing gives exact reported sealed file lengths and version checksums.
- Each block index gives compressed frame length, uncompressed body length,
  row count, and sequence/time bounds. Reading record bodies is unnecessary.
- The collection index gives collection event counts and a membership bitmask
  for each block. It does **not** give a compressed byte contribution for each
  collection, or even per-block per-collection row counts.
- A block's compressed frame is shared. Assigning its bytes in proportion to
  event counts would be an allocation estimate, not a measured disk size.
- A source's matching-block bytes can be measured as a read footprint, but
  footprints overlap. They cannot be summed as independent storage ownership.
- Metadata identifies neither safe deletions nor the space compaction would
  reclaim. Changing contents changes compression and may require rewriting.

## Bounded inspection

`strata/inspect-storage.py` lists at most ten pages, permits at most
20 requests per run, caps each response at 4 MiB and collection-index expansion
at 32 MiB. It reads headers, block indexes, and collection-index tails for the
first, middle, and final listing entries. No block frames, records, media,
Microcosm APIs, or full-file payloads are read.

The successful run used 19 requests and 1,833,965 response bytes. An initial
attempt to read whole footers stopped at its cap: the latest footer exceeded
4 MiB. The revised reader skips bloom filters and fetches only the two indexes.
The report records the successful run's budget, not both attempts combined.

Checks: listing checksum matches header identity; header is reread after each
probe; sizes reconcile exactly: compressed frames + frame prefixes + header +
footer = file length. Collection masks have validated dimensions. This does
not recompute the metadata checksum (which includes skipped bloom filters),
and it does not verify data-frame checksums. Multi-page listing is not atomic.

| Listing position | File size | Compressed data | Uncompressed blocks | Metadata + framing | Compressed bytes in shared-namespace blocks |
|---|---:|---:|---:|---:|---:|
| First | 269,735,440 | 269,605,093 | 1,263,753,347 | 130,347 | 29,790,149 (11.0%) |
| Middle | 259,045,260 | 258,889,430 | 1,193,461,650 | 155,830 | 48,675,383 (18.8%) |
| Last measured | 273,237,270 | 268,652,030 | 982,730,290 | 4,585,240 | 268,646,139 (>99.9%) |

These are three concrete examples, not representative samples or archive-wide
compression/ownership estimates. Shared membership includes account-level
sentinels as separate sources. Event-count spheres remain event-count spheres.

## Product and request boundaries

The unlisted preview includes a collapsed “Space behind the spheres” explainer:
measured overall file size plus selectable comparisons for the three files.
Measurement date and scope are visible. The report is a static build input,
not refreshed per visit or by a scheduled task.

Microcosm remains a contextual UFOs link only: **zero API calls from Strata**.
Do not fan out over the namespace inventory, prefetch on pan/zoom, or poll.
A future inline enrichment should be explicitly requested for one selection,
cached, bounded to one in-flight request, and stop on rate limiting rather than
retrying or moving through the inventory. Its time window and observation
coverage must remain distinct from archive storage measurements.

The existing `my-prefect-server/flows/strata.py` already reads changed segment
collection indexes. If full storage attribution/read-footprint indexing is
wanted, extend that existing checksum-driven pass, reusing its decoded masks
and reading the block index once per changed segment. Persist aggregates keyed
by segment version; do not create a second all-archive crawler. Any shared
block total must deduplicate `(segment, checksum, block index)`. No ingestion,
D1 schema, compaction behavior, or production Stream binary was changed here.