Data Recovery Case File · NAS & Network Storage · Mirroring Is the Point
In a Mirrored Pair, Either Drive Holds the Whole Set
His enquiry describes a bad situation with a structural advantage he has half-noticed. Two drives from a mirrored network unit, both sounding wrong on power-up, where "I suspect one has been formatted in error and one may still be intact". Mirroring means each drive carries a complete copy — so a format on one leaves the other holding everything, and the pair's redundancy is exactly what this situation was designed for.
| Media | Two 3TB drives from a mirrored network storage unit — both producing abnormal sounds on power-up; one believed formatted in error |
| Reported situation | Two drives previously configured as a mirrored pair in a network unit · both producing abnormal sounds at power-up · neither visible or usable · one believed formatted in error · the other believed possibly intact · years of photographic content held · owner uncertain of prospects |
| Fault class | Mechanical faults on both members of a mirrored pair — each member independently holding a complete copy; format on one not affecting the other's content |
| Equipment used | Mirrored configuration recognised as giving each member a complete copy · each drive assessed and imaged separately with no shared assumption · laminar flow bench inspection with head and surface assessment before any spin attempt on either · matched donor parts as indicated · volumes interpreted from images independently of the original unit |
The decode: what mirroring gives him, and what it does not
What a mirrored pair actually stores: the same content on both drives simultaneously. Every write goes to both, so each drive holds a complete, independent copy — not half each, and not fragments requiring the other to make sense.
Why that is exactly the right structure for what has happened: a format applied to one member does not touch the other. The second drive holds the entire set on its own, and it can be read without the first being involved at all.
Why a format on the other is also less final than it sounds: a format writes a fresh empty index and marks capacity available. The photographs themselves are not erased and remain in place until overwritten — so even the formatted member is a candidate, and between the two there are two independent routes to the same material.
What complicates it, and it is the real problem: both drives sound wrong on power-up. The format is not what is stopping him — the mechanical condition is, and that applies to the drive he hopes is intact just as much as the other.
Why simultaneous failure of both is less surprising than it seems: drives in a mirrored pair are bought together, run together, spin the same hours, and sit in the same enclosure at the same temperature. They age identically, which is why mirrored pairs frequently fail close together — the redundancy protects against one drive failing, not against both wearing out at the same rate.
Why each must be assessed separately regardless: shared history does not mean identical condition. One may be considerably more recoverable than the other, and since either alone would yield the complete set, the better of the two is what matters.
Why that changes the economics in his favour: only one drive needs to succeed. Two independent chances at the same content is a materially better position than a single failed drive, which is worth knowing before he concludes that years of photographs are gone.
Why the unit itself is not needed: the volumes are interpreted from images rather than reassembled by the original hardware. The enclosure's own format is readable with the right tools, so the failed unit is not an obstacle.
What must not happen: no further power-up of either drive, and no attempt to rebuild the pair. Rebuilding writes across a member — and on a mirrored pair, a rebuild started in the wrong direction would copy the formatted drive over the intact one, which is the one action that would genuinely lose everything.
On the bench
Mirrored configuration was recognised as giving each member a complete copy — every write being applied to both drives, so either alone carries the full set and a format applied to one leaves the other's content untouched, while a format on the affected member replaces the index without erasing content. Each drive was assessed and imaged separately with no shared assumption, common purchase and identical operating hours accounting for near-simultaneous failure. Inspection ran under the laminar flow bench before any spin attempt on either.
The outcome
The mirrored structure recognised as giving two independent routes, each drive assessed separately, and both inspected under filtered air before any rotation. Free assessment, one fixed written figure including VAT, charged per drive, with 50% of parts and labour upfront and the balance only on successful recovery. The decode: in a mirrored pair each drive holds everything, so the format on one leaves the other complete — and even the formatted one keeps its content until overwritten. The obstacle is the mechanical condition, not the format.
A mirrored pair where one drive was formatted
Don't attempt to rebuild the pair — a rebuild started in the wrong direction copies the formatted drive over the intact one, and that's the single action that would genuinely lose everything. Take some encouragement first: mirroring writes the same content to both drives, so either one holds your complete set independently, and a format on one leaves the other untouched. Even the formatted member keeps its content until something overwrites it. Both drives sounding wrong is the real obstacle rather than the format, and it's common — mirrored drives are bought together and run identical hours, so they age at the same rate.
Don't rebuild the pair — call Easy Data Recovery on 028 9002 0144; each member holds a complete copy, each drive assessed and imaged separately, inspected under filtered air before any spin attempt.
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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.