Data Recovery Case File · NAS & Network Storage · The Better Half of the Problem
When the Enclosure Fails and the Members Do Not, the Volume Is Assembled Elsewhere
His enquiry states the situation plainly and adds a useful disclaimer. A two-drive home network unit running a mirror, where "the device failed — the disks appear okay, but my knowledge is very limited" — domestic use, mostly photographs. Distinguishing the appliance from the disks is exactly the right instinct, and if it holds, this is the most straightforward kind of network storage failure there is.
| Media | Two-drive network storage appliance configured as a mirror — appliance not functioning; member disks apparently unaffected; domestic photographic content held |
| Reported situation | Two-drive network appliance in domestic use · mirrored configuration · appliance ceasing to function · member disks believed unaffected · owner describing limited technical knowledge · photographic content sought |
| Fault class | Appliance failure with members intact — volume readable offline once the appliance's own format is interpreted; mirror providing two complete copies |
| Equipment used | Appliance failure distinguished from member failure before any action was taken · both members imaged individually write-blocked before any interpretation · appliance volume manager and filesystem identified from on-disk structures · volume assembled offline from the images · members compared to establish which is more current |
The decode: why this is the good version, and what not to do meanwhile
Why an appliance failure is better news than a disk failure: the appliance is replaceable and the disks are not. Power supplies, controller boards and network interfaces all fail without touching what is stored.
What a mirror gives him on top of that: two complete copies. Each disk holds everything, so even a failure affecting one member leaves a full copy on the other.
Why the disks nonetheless cannot simply be plugged into a computer: the format is the appliance's own. Network units run their own operating system and write volumes in a format desktop systems do not implement.
What a computer will do when shown one: offer to prepare it. Presented with a filesystem it cannot read, a host reports the disk as unformatted and invites initialisation.
Why that offer is the single thing to refuse: it writes. Accepting replaces the appliance's structures with new empty ones, and that is the one action that would turn this into a difficult case.
Why buying an identical appliance is not the obvious fix it appears: it may not adopt the disks. Some units accept an existing set and some initialise them on first start, and which is which is not worth discovering with the only copy.
How the volume is read instead: offline. Both members are imaged and the volume assembled from the images, with the appliance out of the picture entirely.
Why both members are imaged rather than just one: mirrors diverge. If one member dropped out earlier than the other, the two hold different versions, and comparing them establishes which is current.
Why the limited technical knowledge he mentions changes nothing: he has already made the right observations. Noticing that the appliance failed rather than the disks is the distinction that matters.
What must happen now: label each disk with the bay it came from. Position matters to reconstruction and is easy to lose once drives are out.
On the bench
Appliance failure was distinguished from member failure before any action was taken — power supplies, controller boards and network interfaces failing without affecting stored content, while a mirror leaves each member holding a complete copy. Members nonetheless carry the appliance's native format, which desktop systems do not implement and therefore report as unformatted, inviting initialisation. Both members were imaged and the volume assembled offline, with divergence between them established by comparison.
The outcome
Appliance failure distinguished from member failure, both members imaged individually, and the volume assembled offline from the images. Free assessment, one fixed written figure including VAT, charged per drive, with 50% of parts and labour upfront where a drive has to be opened. The decode: this is the good version of a network storage failure. The box is replaceable and your disks are not — and a mirror means each of them holds everything.
When a network storage box fails but the disks seem fine
Don't connect the disks to a computer and accept anything it offers — a host shown an appliance's native format reports it as unformatted and invites you to initialise it, which replaces the structures holding your volume. Don't buy an identical appliance and insert them either: some units adopt an existing set and some initialise it on first start, and that isn't worth discovering with your only copy. Label each disk with the bay it came from before removing them.
Don't initialise anything — call Cambridge Data Recovery on 01223 655015; appliance failure distinguished from member failure, both members imaged, volume assembled offline from the images.
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Our case files are drawn from genuine enquiries received by our laboratory over the past ten years, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery procedure our engineers apply to that fault, using the equipment listed.