Data Recovery Case File · NAS & Network Storage · RAID or Two Separate Disks?

Two-Bay Enclosure With No Power: What to Ask First

His enquiry was brief, businesslike and left one crucial thing unstated. "We have an external twin-drive enclosure with two 10TB hard drives that doesn't seem to get power any more. Can you advise and quote for repair please?" Twenty terabytes across two disks in a desktop enclosure, and the question that decides everything about this job is not what has failed — it is how those two drives were configured. A twin-bay enclosure can be running as two independent disks, as a mirrored pair, or as a striped volume, and those three arrangements produce three completely different recoveries with three different risk profiles. Before any of that, though, there is a test costing nothing that resolves a surprising number of these cases, because desktop enclosures of this kind fail in one place more than any other.

The decode: the cheap test, and the three configurations

The cheapest test first: desktop enclosures of this size use an external mains power supply — a separate brick with a barrel connector — and those fail far more often than anything inside the case. They are the highest-stress component, they run warm, and they are cheap. So the first question is whether the supply is delivering its rated output at all. Substituting a known-good supply of the correct voltage, polarity and current rating is a legitimate test, and it resolves a meaningful proportion of dead enclosures for the price of a replacement brick. The emphasis on correct specification is not a formality: a supply of the wrong voltage will damage the electronics behind it, which is a self-inflicted version of a case elsewhere in this archive.

Why the configuration question outranks the fault: if the enclosure is genuinely dead, the drives come out — and what happens next depends entirely on how they were arranged. Two independent disks: each is a complete, separate volume, readable on its own, and this becomes two straightforward jobs. Mirrored: each disk holds a complete copy of everything, which is the most forgiving arrangement possible — either member alone can supply the whole dataset. Striped: every file is divided across both members in alternating chunks, so neither disk holds a complete anything, both are essential, and the layout must be reconstructed before a single file can be read. On a 20TB pair the difference between the last two is the difference between a routine read and a full array reconstruction.

How to find out: he may not know, and that is normal — enclosures are frequently configured once at setup and never thought about again. It does not need to be established in advance, because the configuration is determined by analysis of the drives themselves: each member is imaged individually first, and the layout is then derived from the images by testing candidate arrangements against the filesystem's own structures. What he should avoid is guessing and acting on the guess.

The thing that must not happen: whatever the configuration, the members must not be initialised, formatted or rebuilt in an attempt to make them work. Connecting a striped or mirrored member to a computer often produces an offer to initialise it — the disk carries a filesystem the host does not recognise, or none it can parse — and accepting that on a member of a striped set destroys the layout, while accepting it on a mirror destroys a complete copy.

On the bench

The power supply was checked against specification before anything was dismantled, since a dead brick is both the likeliest cause and the cheapest outcome. With the enclosure confirmed as the fault, both members were removed, labelled by bay, and imaged individually write-blocked on the Atola TaskForce 2 — both of them, rather than one, because the configuration was not yet known and an assumption at that stage is the most expensive kind. The arrangement was then determined from the images by analysis, and where the pair proved striped, the volume was reassembled offline from the copies with member order, block size and offsets derived rather than guessed. The contents were verified by opening and delivered on fresh media.

The outcome

The supply eliminated, both members imaged individually, the configuration established by analysis and the contents verified and delivered. Free assessment, one fixed written figure including VAT; where a drive has to be opened, 50% of parts and labour is payable upfront with the balance only on success — otherwise no recovery, no fee. The decode, for anyone with a dead twin-bay enclosure: test the external power supply first, with one of the correct voltage, polarity and rating, because those bricks fail more often than anything inside the case; then establish how the two drives were configured, because independent, mirrored and striped are three different recoveries and the last requires both members and a reconstructed layout; and never initialise, format or rebuild a member to make it readable — on a stripe that destroys the layout, and on a mirror it destroys a full copy.

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.