Data Recovery Case File · NAS & RAID · The Copies That Lied

Hot to the touch, corrupt on arrival: an overheating NAS pair, the silent failure inside "successful" copies, and the recovery that verified everything

His response to the emergency was close to exemplary, which makes the sting in his enquiry's tail all the more instructive. The two-drive Seagate NAS had turned sluggish; on inspection, one 3TB drive was "almost too hot to touch," its neighbour — sitting right beside it — thoroughly heat-soaked too. He powered the unit down immediately and removed both drives: exactly right. Then the savvy continued: knowing the NAS spoke Linux internally, he mounted the drives on Windows through an EXT3 reader — drive one wouldn't mount at all; drive two mounted, and he copied across about 50% of the data. And then the sting: among the recovered files, some arrive corrupt — Office complaining that documents and spreadsheets can't be opened. Copies that completed, contents that hadn't. That gap is this page's whole subject.

Two decodes: what heat does, and why "copied" isn't "correct"

The heat. A drive running almost too hot to touch is far outside its design envelope — a failed fan, blocked airflow or a failing component turning the enclosure into an oven — and sustained heat degrades everything at once: electronics drift, mechanics expand out of tolerance, and the read channel's margins — the delicate business of telling signal from noise — erode first. His two drives showed the dose-response curve perfectly: the hotter unit degraded past serving its filesystem at all; the neighbour, cooked secondhand, still answered but no longer answered reliably. Which sets up the sting. A copy operation trusts what the drive serves: when a heat-stressed read channel returns plausible-but-wrong data — errors slipping beneath the drive's own weakened correction — the copy completes, the progress bar fills, the file lands at its destination byte-for-byte faithful to a misread. Nothing warns. The corruption only surfaces when Office tries to parse the file and finds internal structure that no longer adds up. His 50% wasn't 50% recovered; it was 50% transferred, with an unknown fraction silently broken — the most dangerous state in amateur recovery, because it feels like success right up until the deadline when a document won't open.

The recovery — reads that prove themselves

Both drives were imaged on the PC-3000 the way heat casualties demand: error-managed, sector by verified sector, the equipment refusing the "plausible" answer and re-reading until responses stabilised — marginal regions negotiated in patient bounded passes rather than trusted on first reply. Drive 1's unmountable filesystem reconciled cleanly on its image, its unreadability having been the read channel's fault rather than the structures'; drive 2's image superseded every byte of his desk-side copying. From the pair, the NAS's EXT3 volume was extracted whole — and then the step his sting made non-negotiable: verification by parsing — documents opened, spreadsheets loaded, archives tested across the estate, so that "recovered" meant opens correctly, not transferred completely. The previously-corrupt files came back clean from the properly-read image; the honest residue — content degraded beyond even managed re-reading — was itemised by name. Delivered on new, well-ventilated storage, with the retired pair's thermal history closed out in the report.

Outcome

Both drives recovered, the corrupt copies replaced with verified ones — and the lesson his excellent triage earned the right to teach: from a heat-stressed or failing drive, a completed copy is a claim, not a fact. Verify by opening, and treat any corruption in the sample as evidence the whole copying method is compromised — the moment to stop copying, not to copy harder. His prompt shutdown remains the case's other star: heat damage is cumulative, and every minute at that temperature was spending both drives; killing the power froze the bill. Add the prevention his NAS was begging for — a unit whose drives you can't touch has been shouting for weeks in temperatures its logs record and nobody reads — and the whole genre becomes avoidable: dust the vents, hear the fan, and let the first sluggish afternoon be the day you check, not the day you 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.