When a Simple Restart Turns Into a Disappearing Act
The system was running fine.
You applied updates… or simply rebooted… or the power blinked for a second.
Nothing dramatic.
Then the server came back online — and your RAID 5 virtual disk wasn’t there.
No mount.
No filesystem.
Just an empty controller screen where the array used to be.
This symptom is far more common than vendors admit.
And it almost never means the data is gone — only that the controller can’t safely validate the identity of the array after an unexpected shutdown.
What You See
- Virtual disk completely missing from the controller BIOS
- Controller reports: “No VD Present”, “Virtual Disk Not Found”, or “Incomplete configuration”
- All drives show Online, Ready, or Unconfigured Good (even though they belong to a RAID)
- Logs may show:
- “Disk group invalid after power event”
- “Foreign configuration detected”
- “Cache metadata mismatch”
- “Degraded/incomplete array — hidden for safety”
- OS boot logs show no block device for the RAID
Why It Happens
1. Cache/NVRAM Epoch Drift
During a power loss, cached writes may not have reached the disks.
The controller then sees a metadata mismatch between memory and disk and hides the array.
Ref: TN-R5-001 §6, §8
2. Partial or Interrupted Background Operations
If a background initialization or parity check was in progress, it may have stopped mid-stripe.
To avoid writing bad parity, the controller removes the VD from service.
Ref: TN-R5-001 §3, §6
3. Silent Latent Sector Errors Exposed on Reboot
The reboot forces the controller to read metadata from disks that haven’t been touched in years.
Any unreadable sector during this step can cause the array to be dropped.
Ref: TN-R5-001 §3
4. “Foreign” Signatures Introduced Temporarily
If drives power up out of order or take too long to spin up, the controller may believe the set is foreign or incomplete.
Ref: TN-R5-001 §4
5. Controller Safety Policies Hiding the VD
Modern firmware will hide an array if it detects:
- incomplete metadata
- inconsistent parity
- mismatched timestamps
- missing boot sectors
Ref: TN-R5-001 §8
This behavior is protection — not destruction.
What NOT To Do
- Do NOT import the foreign configuration yet
- Do NOT initialize the virtual disk
- Do NOT force drives online
- Do NOT recreate the array “with the same settings”
- Do NOT swap controllers or backplanes
These steps overwrite original metadata and dramatically reduce recovery probability.
What You CAN Do
- Power down the system cleanly
- Clone every member drive (failed, surviving, and “ready” disks)
- Capture controller config / logs / NVRAM state
- Map drives to physical slot + serial + WWN
- Verify metadata signatures across all drives
- Compare timestamps and stripe-alignment consistency
- Recreate the virtual RAID in software for offline validation
- Recover the filesystem without touching the controller’s unsafe rebuild path
When done correctly, most “disappeared” RAID 5 arrays are fully recoverable.
Diagnostic Overview
- Array Type: RAID 5 — Single Parity Set
- Controller State: Virtual Disk Missing After Power Event
- Likely Cause: Cache Metadata Drift or Latent Sector Errors Exposed at Boot
- Do NOT: Import Foreign Config, Initialize, or Force Drives Online
- Recommended Action: Clone All Members, Capture Logs, Validate Metadata, Reconstruct Layout Offline
RAID Triage Center – RAID 5 Triage – RAID 5 Technical Notes