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Journey: Demote Idle Documents to Cold

The economics lead takes a policy from a merge request to every eligible object, and learns at the first ring that the corpus disagrees with the model.

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Storage economics lead policy v42 Goal — Move documents idle for 90 days to cold, net positive Trigger — Quarterly bill 11% over plan; warm tier at 81% Done when — Full rollout, realised delta within 10% of shadow 1 · Draft 2 · Shadow 3 · Dry run 4 · First ring ◆ moment of truth 5 · Widen 6 · Score What they do Writes policy in CUE Runs shadow on corpus Dry run on 1% sample Approves 0.1% ring Reads realised delta Scores at day 90 System behind it Policy repo Shadow runner Break-even evaluator Ring controller Cost ledger Decision records How it feels Confident Unsure Anxious Where it hurts Which window per class? Projects 38%, not 45% Re-read rate 4.1% Early deletes creeping What the platform gives Ladder does the arithmetic Bill delta, 0 bytes moved Losing objects named Ring halts itself Revert free for 24 h Predicted vs realised Journey — Economics Lead Demotes Idle Documents to Cold v 1.0 · owner Storage Platform Architecture · date 2026-09

The worst moment

  • The first ring. At 0.1% of eligible objects, 4.1% of what was demoted is read again by a promoting class within 14 days, against a 1.5% gate. Almost all of it is quarter-end finance workbooks: idle for 97 days and due to be reopened in the next fortnight. The policy used the 90-day document window; that workspace class should have been declared periodic.
  • Without an automatic gate the lead would be deciding, alone and at speed, whether a number is noise. With one, the ring halts itself and the question becomes which object class was mis-declared.

What the architecture owes this journey

  • Shadow mode over the whole corpus, so the first number the lead sees is a projected bill delta, not a moved byte (ADR-22).
  • A dry run that really copies a 1% stratified sample to scratch space, so request cost and throughput are measured rather than estimated.
  • A 24-hour release hold, so reversing a bad ring is a catalogue pointer flip rather than a retrieval (ADR-03).

Numbers

  • Rings at 0.1%, 1%, 10% and 100% of eligible objects, each held for at least 72 hours. The gate reads re-read rate for immediate destinations, wrong-tier rate for delayed ones, and the charge ratio for both. No policy may move more than 2% of objects or 1.5 PB in any seven-day window.
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Solution Architecture v1.0 · Storage Platform Architecture · 2026-09 · 31 views · open source, fully on-premises04-journey-roll-out-a-demotion-policy