Specialist · Synology recovery
Synology's scariest message covers three completely different failures — a RAID losing members, LVM losing its map, or btrfs losing its tree — that all look identical on screen and need opposite treatment. Which is why the only universal first move is the undramatic one: power the DiskStation down and keep your finger off Repair.
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| The situation | What it means | First move |
|---|---|---|
| DSM: Volume Crashed | RAID, LVM or btrfs has failed — three suspects, one message | Power down; don't click Repair |
| DSM: Storage Pool Degraded | A member is out but the pool limps on — redundancy already spent | Every running hour raises stakes |
| The DiskStation itself is dead | The array lives on the drives, not the box | One of the happier diagnoses |
| A rebuild onto a new drive stalled or 'crashed' | The rebuild's marathon read found a second marginal member | Stop; images decide now |
| Drives moved to a PC, which offers to format them | Windows can't read Linux NAS structures — normal | Decline everything |
| Ransom note where the shares used to be | A NAS strain has been through | Photograph, power down, our ransomware page |
Your device is logged with its own case reference the moment it arrives. An engineer assesses the fault, confirms what's actually recoverable, and you get a fixed price in writing — no diagnosis fee, no obligation, and no paid work until you say go.
Each drive is imaged with bad sectors mapped — the DiskStation never gets the chance to resume a rebuild, and the btrfs tree's historical roots are preserved exactly as the failure left them.
On the images: slices identified, each mdadm array assembled, LVM's map read, and the btrfs or ext4 volume opened read-only — layer by layer, in the only order that works.
Crashed-at-btrfs, crashed-at-LVM and crashed-at-RAID get their specific repairs on the reconstruction — including walking btrfs back to an earlier intact tree where the newest one is damaged — and the shares verified before sign-off.
Before you pay the recovery fee you approve a full listing of what came back. Your data returns on new media with free return postage, and the case only closes once you've confirmed everything opens on your side.
The architecture fact that decides these cases: a mixed-capacity SHR volume is not one array — it's several mdadm arrays across per-drive slices, glued by LVM, wearing one filesystem. Recovery that doesn't unwind those layers in exact order finds nothing; recovery that does routinely brings back volumes the DiskStation itself pronounced crashed.
Two 4TB and two 8TB drives, one failure, and a rebuild DSM attempted overnight that ended in Volume Crashed. Under the hood: three separate mdadm arrays, two healthy, one degraded-but-derivable. Assembled off-box in order, the btrfs tree stepped back one generation, and every share returned.
Very unlikely. Crashed means DSM can no longer assemble the stack — because the RAID lost members, LVM's metadata broke, or the btrfs tree corrupted. Those are three different, mostly recoverable failures; the message just can't tell you which. Powering down preserves all three possibilities.
No. SHR is standard Linux underneath — mdadm software RAID across partition slices, pooled with LVM, formatted btrfs or ext4. It reassembles on an ordinary workstation from drive images; what it punishes is tools and people who expect one flat array.
Not before the members are imaged. The rebuild reads every sector of the ageing survivors — the exact stress that produces second failures — and can overwrite the historical filesystem roots that recovery falls back on. Image first; then the same rebuild becomes risk-free.
Often partially or fully, depending on the strain — NAS-targeting campaigns have hit internet-exposed boxes for years, and snapshots, replication targets and free-space remnants all get checked. Photograph the note, power down, and start with our ransomware page's routes.
Every restart of a damaged device costs data. Open a case first — the diagnosis is free either way.