TN-R5-006 — Why Rebuild Retries Compound Damage
0. Purpose and Scope
This note explains why repeated rebuild attempts rapidly collapse RAID 5 recovery probability.
1. Non-Atomic Rebuild Behavior
Rebuilds proceed stripe-by-stripe, rewriting parity continuously.
A failed rebuild leaves parity partially altered.
2. Compounding Effect of Retries
Each retry:
- Rewrites additional stripes
- Introduces new inconsistencies
- Narrows reconstruction options
Damage accumulates non-linearly.
3. Misleading Controller Feedback
Controllers rarely warn that parity has diverged.
Each attempt appears “reasonable” — until recovery becomes impossible.
4. Key Rule
A failed rebuild should stop all activity — not trigger another attempt.