Data Recovery Case File · Portable Drives · Check the Other One First

He Did the Right Thing, and Bought Both on the Same Day

His enquiry describes an arrangement most people never make. A 4TB external no longer responding, where "I have two external drives of the same model, so to have a backup, the second" holds a copy. That is a genuine backup and it changes everything about this enquiry — but the detail that makes it convenient is also the flaw in it, and both are worth saying.

The decode: verify the copy, then read the warning in it

The first thing to do, and it costs nothing: check the second drive properly. Not that it mounts — open several files across different folders and confirm they render. A backup that lists correctly and contains damaged content is a failure mode this archive sees constantly, and it is only ever detected by opening something.

The second thing: establish how current it is. A manually maintained copy is as recent as the last time somebody remembered, and the gap between that date and now defines exactly what is missing. Everything before it is safe; everything after it is the actual job, which may be small enough to change the decision entirely.

Why this reduces the case rather than ending it: if the copy is complete and current, there is nothing to recover and he should be told so plainly. If it is a month old, the work is scoped to a month. Either outcome is better than treating the failed drive as though it held the only copy, which is the assumption most enquiries carry.

Now the flaw, and it is worth knowing before he replaces anything. Two drives of the same model, bought together, come from the same production period and frequently the same batch. They have identical designs, identical firmware, and — if used similarly — comparable wear. Whatever caused one to fail is disproportionately likely to affect the other, on a similar timescale.

Why that matters right now: the surviving drive is the one holding everything, and it is the same age and model as the one that just failed. It should be treated as the more urgent device rather than the safe one — its contents copied somewhere else promptly rather than left as the sole copy of a lifetime.

What to check on it, free: its self-reported statistics. Reallocated sectors, pending sectors, powered hours — a query taking seconds. If the survivor is reporting the same wear as its twin, that is a warning worth acting on before it becomes a second enquiry.

What to do differently next time: keep the arrangement and break the matching. Two drives of different makes, bought at different times, provide the same convenience without the shared failure mode.

On the bench

The second drive was verified by opening files before any work on the first — a copy that lists correctly while containing damaged content being a failure mode detectable only by opening something. Currency of the copy was established, the gap between the last update and the present defining precisely what is missing. Self-reported operating hours were read on the surviving drive, matched drives from one batch sharing design, firmware and wear characteristics. Recovery was scoped to material absent from the copy.

The outcome

The copy verified by opening before any work, its currency established and recovery scoped to the gap. 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: check the second drive by opening files rather than by seeing it mount, and establish how recent it is — that gap is the whole job. Then treat the survivor as urgent, not safe: two drives bought together share a batch, a design and a wear curve.

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.