Data Recovery Case File · Formatted & Logical Faults · The Spare Is at the Other End
A Volume Keeps Its Backup Descriptor Far From the Original, So Losing Both Means Something
His enquiry reports a finding precise enough to reason from. A family laptop drive with corruption, removed and connected to another machine to run a consistency check, where "the result was that the first and second boot sectors were unreadable or corrupt." Those two structures are deliberately kept apart — one at the start of the volume and its duplicate near the end — so losing both is not simply losing one thing twice.
| Media | Laptop hard drive removed and connected externally — consistency check reporting both the primary and backup volume descriptors as unreadable; photographic and document content sought |
| Reported situation | Family laptop drive suffering corruption · drive removed by the owner · drive connected to a second machine · consistency check run · check reporting the primary volume descriptor unreadable · check reporting the backup descriptor also unreadable · photographs and other files sought |
| Fault class | Both volume descriptors unreadable — structures held at opposite ends of the volume, so simultaneous loss indicates either widespread read failure or damage at both extremes; content regions unaffected either way |
| Equipment used | Descriptor placement assessed to interpret the double failure · no further checking or repair permitted · drive addressed with imposed timeouts outside any host storage stack · surface behaviour sampled at both volume extremes before full imaging · volume parameters reconstructed from filesystem metadata rather than from either descriptor |
The decode: why the pairing matters, and what running the check risked
What a volume descriptor does: it identifies everything. A small structure at the start of a volume states its size, its arrangement and where its directory begins, and nothing can be interpreted without it.
Why a duplicate exists at all: the original is vulnerable. It sits at the very beginning of the volume, which is where formatting, partitioning and boot code all write.
Where the duplicate is placed: as far away as practical. The backup is written near the end of the volume, precisely so that whatever destroys one is unlikely to reach the other.
Why both failing is therefore informative: a single local event should not do it. Damage at the start of the volume does not reach the end, and vice versa.
What the two remaining explanations are: widespread read failure, or two separate events. Either the drive cannot reliably return data anywhere, or the extremes of the volume have both been affected.
Why the first is more likely on a drive described as corrupt: degradation is not localised. A drive returning errors across its surface fails to read both descriptors for the same reason it fails elsewhere.
Why that reading is not as bad as it sounds: unreadable in one attempt is not unreadable. A consistency check makes a limited number of attempts, and a region that fails there may return across repeated passes.
Why the descriptors are not essential anyway: the volume describes itself elsewhere. Filesystem metadata throughout the volume permits its parameters to be reconstructed without either copy.
Now the risk he took without knowing: the check writes. A consistency check that finds a repairable inconsistency repairs it, by writing new structures over the old ones.
Why he was fortunate here: it could not proceed. A check unable to read the descriptors had nothing to work from, so it reported rather than rewrote.
On the bench
Descriptor placement was assessed to interpret the double failure — a volume descriptor stating size, arrangement and directory location, with its duplicate deliberately written near the volume's end so that damage reaching one is unlikely to reach the other. Simultaneous failure therefore indicates widespread read difficulty or two separate events, the former being likelier on a degrading drive. Volume parameters were reconstructed from filesystem metadata rather than from either descriptor.
The outcome
Descriptor placement assessed to interpret the finding, further checking stopped, and parameters reconstructed from metadata rather than either copy. 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: those two structures are kept at opposite ends deliberately. Both failing points at the drive rather than at one event — and unreadable in one attempt is not the same as unreadable.
When a check reports both boot sectors gone
Don't run it again. A consistency check that finds something repairable repairs it, writing new structures over the old — you were fortunate that it couldn't read enough to proceed. Read the finding properly, though: the backup descriptor is written near the end of the volume specifically so that damage reaching the start won't reach it, so both failing points at widespread read difficulty rather than one event. And a region that fails a check's limited attempts often returns across repeated passes.
Run nothing further — call Cambridge Data Recovery on 01223 655015; descriptor placement assessed to interpret it, both volume extremes sampled, parameters reconstructed from metadata rather than either copy.
Request a quote online →
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.