When the Hardware Looks Fine but the Logic Refuses to Trust It
A RAID 50 failure is scary enough when you see red lights and failed drives.
It’s even worse when everything looks healthy:
- all drives show Online / OK
- SMART status is Normal
- no obvious “Failed” labels
…and yet:
- the RAID 50 virtual disk is Offline
- no volumes mount
- users are standing over your shoulder
This page explains why a RAID 50 can go offline even when every drive appears fine — and what you must do next to avoid turning a logical fault into permanent data loss.
What You See
- The RAID 50 virtual disk or logical drive is reported as:
- Offline
- Missing / Not Present
- Inactive / Failed
- Each physical disk in the set shows:
- Online / Good / OK
- Or at worst: Predictive Fail, but not outright Failed
- Controller BIOS or management utility may show:
- All members present and spinning
- One RAID-5 group in an “inconsistent,” “partial,” or “unknown” state
- Conflicting foreign configuration messages on one or more members
- Operating system:
- No usable volume visible
- Or a volume that appears but cannot mount or reports as RAW
Why It Happens
RAID 50 depends on all of its RAID-5 groups agreeing on layout, parity epoch, and membership.
If the disks are physically fine but the virtual disk is offline, the problem is almost always logical, not physical:
- Controller detects metadata disagreements between RAID-5 groups
- One group’s parity epoch is newer or older than the other
- One group’s layout (stripe size/rotation) doesn’t match
- A recent power event or unsafe shutdown caused cache / NVRAM drift
- One group committed cached writes; another did not
- The controller can’t guarantee parity correctness across groups
- A drive was moved, reseated, or replaced in a way that changed:
- Slot order
- Member identifiers
- Foreign vs native config state
- Background tasks (verify, patrol read, init) were interrupted
- One group paused mid-cycle
- The other group did not, leaving them out of sync
- The controller deliberately refuses to assemble the VD
- It prefers an offline, recoverable state over an online but corrupt one
From the outside, drives all “look healthy.”
Inside the controller, the math no longer adds up across stripe groups.
What NOT To Do
When everything looks physically fine, it’s tempting to “help” the controller by forcing things back online.
Those are the exact actions that commonly destroy RAID 50 arrays beyond repair.
Do not:
- Do not force the virtual disk Online “just to see what happens.”
- Do not force drives Online in a group that shows “inconsistent” or “foreign.”
- Do not clear foreign configurations until all metadata has been captured.
- Do not delete and re-create the RAID 50 with “same settings” — that overwrites critical metadata regions.
- Do not run filesystem repair tools on a volume that just came back after being offline.
- Do not hot-pull and reseat drives trying to “wake up” a stripe group — that risks drive-order and identity mismatch.
Every one of those actions removes clues we need to reconstruct the stripe groups correctly.
What You CAN Do
These steps preserve both physical media and logical relationships so a recovery engineer can reverse the offline state safely:
- Collect full documentation:
- Record the current controller status screens
- Capture which drives belong to which RAID-5 group
- Note any “inconsistent,” “partial,” or “foreign” flags
- Power down cleanly:
- Stop I/O
- Shut down the host gracefully if possible
- Avoid repeated hard resets or power cycles
- Label everything:
- Slot → serial number → WWN for each drive
- Mark group membership if the controller shows it
- Clone all drives bit-for-bit:
- Every “healthy” drive still may have latent sector errors
- Work from clones, not originals, for any reconstruction
- Extract metadata:
- From controller config exports
- From NVRAM/cache dumps (if available)
- From on-disk RAID headers on each member
- Rebuild virtually:
- Reconstruct each RAID-5 group independently on images
- Validate parity and stripe alignment per group
- Recreate the RAID-0 mapping across those validated groups
- Only then bring a virtual RAID 50 online, offline from the controller, for filesystem repair
This is the process ADR uses for “offline but healthy drives” RAID 50 cases — treating it as a logical disagreement, not a simple hardware swap.
Diagnostic Overview
- Array Type: RAID 50 — Multiple RAID-5 Groups Striped Under RAID-0
- Controller State: Virtual Disk Offline / All Members Reporting Online or Present
- Likely Cause: Metadata or Epoch Drift Between Stripe Groups, Not Physical Disk Failure
- Do NOT: Force VD or Members Online, Clear Foreign Configs, Recreate Array, or Run Filesystem Repairs
- Recommended Action: Document State, Clone All Members, Extract Group Metadata, Virtually Rebuild RAID-5 Groups and Then RAID-0 Layer