When the Array Comes Back Online — but Data Doesn’t
A RAID 50 array can appear “healthy” after a rebuild even when the underlying block structure is no longer coherent. The volumes mount, the folders look normal, and SMART data may show no failed drives — yet files return CRC errors, databases fail to open, VMs refuse to boot, or backups validate incorrectly.
That’s because a rebuild can complete without restoring stripe cohesion across all RAID-5 groups, leaving the filesystem to read block ranges that no longer match.
This page explains what corruption-after-rebuild really means, what the controller is protecting, and how to proceed without losing remaining recoverable data.
What You See
- Array is Online
- Volumes mount normally
- SMART shows no failed drives
- Applications report file-level corruption
- Databases return validation errors
- VMs blue-screen or fail to boot
- Backups restore but contents are wrong or incomplete
- Logs may show:
- “Recovered errors”
- “Consistency check passed”
- “Media verification deferred”
- No error at all
What’s Actually Happening
In RAID 50, each RAID-5 group rebuilds independently.
But the final RAID-0 stripe that spans all groups is not fully validated after rebuild.
Corruption occurs when:
- One RAID-5 group rebuilt using stale or survivor-only parity
- Timing drift caused stripe ranges to reconstruct out of order
- A latent unreadable sector forced the controller to “guess” missing blocks
- One group completed rebuild later than others
- Cross-group parity no longer matches after the array is brought Online
The result:
The filesystem is intact, but the data beneath it is not.
This is block-level corruption, not a filesystem problem.
What Not To Do
These actions overwrite salvageable data and make recovery dramatically harder:
- Do not run CHKDSK /f or /r
- Do not run FSCK or VMFS repair tools
- Do not run vendor “consistency check”
- Do not perform Storage vMotion
- Do not copy large amounts of data
- Do not replace more drives or re-run a rebuild
- Do not clear foreign metadata
Any of these may commit corrupted stripes to disk permanently.
What To Do Instead
- Stop all write activity immediately
- Capture controller logs if possible
- Keep the system powered on but idle
- Do not attempt file repair tools
- Do not migrate or export VMs
- Contact ADR before taking corrective action
Once the OS begins trying to “fix” what it believes is a filesystem issue, it overwrites the only remaining valid parity relationships.
How ADR Fixes It Correctly
ADR uses a forensic-safe recovery workflow designed specifically for nested parity arrays:
- Full member signature and order verification
- Stripe-level comparison across all RAID-5 groups
- Cross-group parity validation to locate timing drift
- Virtual RAID reconstruction (no controller writes)
- Read-only imaging of all members
- Identification of misaligned or overwritten block ranges
- Logical rebuild of the volume using verified parity math
This approach avoids the file-system-destroying overwrites that occur when the controller attempts another rebuild or consistency check.
Diagnostic Overview
- Array Type: RAID 50 — Multiple RAID-5 Groups Behind RAID-0
- Controller State: Rebuild Completed / Filesystem Present but Corrupted
- Likely Cause: Cross-Group Stripe Misalignment or Parity Divergence
- Do NOT: Run CHKDSK, FSCK, VMFS Repair, or Consistency Checks
- Recommended Action: Freeze Writes, Validate Stripe Cohesion, Use Offline Virtual Reconstruction