# Changelog 2026-07-09 -- DC-DC (VR1) originating design

Delivery from the main-chat DC-DC planning stream. Grounded on
`openstack-caracal-dc-dc` HEAD 8813efc (seed-verified). All decisions PROPOSED --
this is a design/plan deliverable, not an implementation. Under blanket approval this
changelog is the review surface: what, why (evidence), and how to revert, per item.

## Items

1. ADD `docs/dc-dc-buildout-design.md` -- originating buildout design for the virtual
   regional two-DC test env (VR1), Phase 0-6 spine, gates, D-refs, shim register, DR drill
   skeleton, host/disk/MTU plan.
   Why: the mission deliverable; no prior DC-DC design doc existed.
   Revert: delete the file.

2. ADD `docs/dc-dc-D100-D110.append.md` -- append fragment carrying PROPOSED decisions
   D-100..D-110 for concatenation onto `docs/design-decisions.md`.
   Why: encodes the settled DC-DC inputs as append-only D-entries; fragment (not direct
   edit of design-decisions.md) keeps the overlay a clean documented append.
   Revert: delete the fragment; if already appended to design-decisions.md, remove the
   D-100..D-110 block (append-only, so a tail trim) and re-run ledger-scan.

## Grounded corrections captured (not silent)

- D-052 "metal-internal may-cross-fiber" refined to DC-local for the independent-cloud
  topology (only replication crosses). Evidence: D-052 text (stretched-cloud assumption) +
  independent-Keystones topology.
- D-057 provider-vip plane NOT carried -- reverted by D-060 (Pattern A). Only the
  root-cause br-ex discipline is carried. Evidence: D-057 live status header.
- DR-seed v4 replication carrier (10.12.36.0/22) superseded -> IPv6-only ULA. Evidence:
  operator ruling + D-101 family matrix.
- No IPv6 literals hardcoded -- ULA /48, per-DC GUA carve, DC2 v4 supernet are
  NetBox-authoritative. Evidence: repo grep found no committed authoritative literals.

## Landing (operator)

Per `docs/dc-dc-buildout-design.md` Section 11: append the fragment to design-decisions.md,
run `ledger-scan.sh` (expect D next-free 111), add a main-chat ledger-fence line,
`repo-lint.sh` (ignore >099 next-free noise), commit.

## Open for redline

Ceph size=3 vs documented size=2 fallback (Phase-0 disk math); netem link profile;
D-102/D-101 merge; D-109 standalone; metal-admin ULA leg; COS roll-up; mirror sync topology.
See design doc Section 10.
