When One Group Disappears… the Whole Array Goes Dark
A RAID 50 array depends on multiple RAID-5 groups working together in perfect lockstep.
So when you open your controller and see:
- “Stripe group missing”
- “RAID group offline”
- One group showing all members FAILED or MISSING
- Volume status: Offline / Unconfigured / Degraded (Critical)”
…it feels catastrophic — because it is.
But catastrophic doesn’t mean unrecoverable.
It means you’re at the point where the controller stops protecting the data and starts protecting itself.
This page explains what happened, what not to do next, and the one safe path forward.
What You’re Seeing
- One RAID-5 group shows as Missing, Failed, or Offline
- The entire RAID-50 virtual disk is offline, even though other groups look normal
- Some drives show Foreign Config, Predictive Fail, or Unconfigured Bad
- Disk LEDs look normal — but the group is gone
- A rebuild refuses to start, or the “Rebuild” option is disabled
Why It Happens
A RAID 50 array is a nested architecture:
- RAID 0 (outer layer) — stripes across
- Multiple RAID 5 groups (inner layer) — each must tolerate exactly one failed drive
That means:
If you lose an entire RAID-5 group… the whole RAID-50 collapses instantly.
The controller cannot reconstruct:
- parity
- stripe ordering
- sector alignment
- block maps
- member distribution
because the upper RAID-0 layer no longer has a complete set of stripes.
The #1 cause: More than one member in a single RAID-5 group dropped or mis-reported.
This can happen from:
- Silent sector errors during rebuild
- Backplane issues
- Slot/mapping drift
- Two drives timing out under load
- NVRAM losing cached metadata
- Controller “panic” during a verify
- Inconsistent drive geometry in one group
What NOT To Do
These actions cause permanent loss, no matter what tools exist:
DO NOT force the drives online
This causes parity overwrite and destroys evidence of the old map.
DO NOT start a rebuild
Rebuild on the wrong member = guaranteed corruption.
DO NOT clear foreign configurations
The “correct” map is in the foreign metadata — once erased, it’s gone forever.
DO NOT initialize or re-create the array
This wipes RAID metadata blocks and overwrites critical regions.
DO NOT reseat drives to see if they come back
Drive reordering = catastrophic on nested RAID.
What You CAN Do (Safe Actions Only)
1. Power down cleanly
Prevents further parity mismatches.
2. Label drives exactly as they are now
Slot → serial → WWN.
Bad labeling = thousands of dollars lost every year.
3. Clone every drive (even “good” ones)
RAID 50 failures often involve silent corruption.
4. Capture controller logs + foreign metadata
This gives us the original RAID-5 member set before collapse.
5. Let a RAID engineer rebuild the group virtually — NOT on the controller
The only safe method:
- Reconstruct each RAID-5 group individually
- Validate parity for each group
- Rebuild the outer RAID-0 mapping
- Recreate the volume offline
- Repair the filesystem from binary evidence
This is the exact process used by ADR’s forensic RAID division.
Diagnostic Overview
- Array Type: RAID 50 — Nested RAID-0 Across Multiple RAID-5 Groups
- Controller State: Stripe Group Missing / VD Offline
- Likely Cause: Multiple Members Lost Within a Single RAID-5 Group
- Do NOT: Force Online, Clear Foreign, Start Rebuild, or Recreate Array
- Recommended Action: Clone All Members, Capture Foreign Metadata, Virtual Rebuild of Each RAID-5 Group