Author: ADR Data Recovery
0. Purpose and Scope
This note documents how RAID 6 arrays lose identity after power events or controller changes.
1. Epoch-Based Metadata
- Controllers track configuration generations (epochs).
- Parity and headers must match epoch state.
2. Causes of Epoch Drift
- Power loss mid-commit
- Cache flush incomplete
- Controller replacement
- Slot or cabling changes
3. Resulting Symptoms
- Virtual Disk Missing
- Foreign Config Detected
- VD present but unmountable
4. Recovery Implication
Identity must be reconstructed logically before parity can be trusted.