What is the demonstrated ceiling of coordinated preservation, and where does it stop?

A subsidiary question under Q-0002 (architectural conditions for survival). §6.1 documents what Tier 2 has actually achieved.

The answer is C-0004: the most sophisticated coordinated preservation systems on Earth — INSDC (3 sites, 53.9T bases since 1980s), wwPDB (4 sites, 250K+ structures since 1971, $23B replacement cost, 100% of recent FDA cancer drug approvals), CLOCKSS, WLCG (1.5 EB, 170+ sites, 42 countries), NOAA NCEI (60+ PB, 4 U.S. locations, survived Hurricane Helene), the IVOA astronomical-archive partnership (30 years) — all operate at Tier 2 via 3-4 institution coordination.

The ceiling is lower than it looks: 3-4 independently-maintained copies is the demonstrated state of the art. Each system is sustained by 1-2 funding streams; the copies are physically independent, but the organizational, political, and budgetary domains governing them often are not. NOAA NCEI's four sites all report to the same agency — a single budget decision can affect all four.

Tier 2 covers a narrow slice of research output. Cross-disciplinary work, small-team studies, underfunded projects, and data types without a community standard have no Tier 2 infrastructure at all. The 73-93% C-0002 baseline is the slice Tier 2 does not reach.