RAID 6 is often described as “RAID 5 with extra safety.”
In practice, it fails for different reasons — and often more quietly.

Dual parity does not eliminate risk. It shifts it.
RAID 6 failures are rarely caused by simultaneous drive loss. They are caused by timing, identity drift, and intervention during reconstruction, when parity confidence collapses without obvious warning.

These Technical Notes document the mechanical boundaries of RAID 6 behavior as observed in real systems across enterprise controllers, mixed disk populations, and interrupted rebuild cycles.

They are not recovery promises.
They are not configuration guides.
They exist to explain why RAID 6 arrays stall, vanish, or return empty after “successful” operations — and why well-intended actions often destroy remaining recovery paths.

What These Notes Are For

The RAID 6 Technical Notes support:

  • Triage after failed or stalled rebuilds
  • Analysis of “Virtual Disk Missing” and foreign configuration states
  • Understanding why dual parity does not guarantee recoverability
  • Preventing destructive rebuilds, parity rewrites, and metadata loss

They assume familiarity with RAID concepts and focus on cause, sequence, and failure boundaries, not introductory theory.

How These Notes Should Be Used

  • Begin with TN-R6-001 for system-level behavior
  • Reference additional notes only when a specific mechanism applies
  • Treat rebuilds, parity checks, and RAID recreation as write-destructive until proven otherwise
  • Preserve original member state before any corrective action

These notes are cited by RAID triage pages, incident analyses, and ADR recovery SOPs.

RAID 6 Technical Notes Index