Data Recovery Case File · Trust, Practice & Honest Limits · The Drives Can Tell You
Identical Drives Are Not Indistinguishable
Her enquiry describes a problem that sounds unsolvable and is not. Two hard drives handed in together: "only one of the drives has data on it, but unfortunately in the process of trying to fix it my husband lost track of which one has the data. I think it's the one marked 1 — the one marked 2 was only bought as spare parts to repair the first one." Neither drive needs to be guessed at, because each carries a detailed account of its own history, and the two accounts will not look remotely alike.
| Media | Two hard drives of matching model — one the original medium and one acquired as a donor; identification lost during an attempted repair |
| Reported situation | Two matching drives submitted together · one holding the required data · one acquired as a source of spare parts · identification lost during an attempted repair by a family member · owner uncertain which is which · repair attempt of unknown extent |
| Fault class | Identification recoverable from device history and content — repair activity of unknown extent to be established on both |
| Equipment used | Both drives identified from serial, manufacture date and self-reported operating history before any work · repair activity established on each · both examined for evidence of opening · original identified by filesystem presence · donor retained as a matched parts source |
The decode: five ways the drives identify themselves
First, and usually decisive — operating hours. Every drive keeps an internal log recording how long it has been powered, how many times it has been started, and its temperature history. A drive that lived in a machine for years reports thousands of hours. A drive bought as spare parts reports whatever its previous life was — almost never the same figure, and frequently a very different one. Reading that log is a query taking seconds.
Second — the manufacture date. Printed on the label and recorded internally. Two drives of the same model bought years apart will differ, and a donor sourced recently for a repair often carries a quite different date from a drive that has been in service.
Third — the serial number. If any record exists of the original machine or the original purchase, it identifies the drive outright.
Fourth, and most conclusive — what is on them. The drive with the data has a filesystem, folders and files. A donor bought for parts has whatever its seller left, or nothing. Reading the first portion of each drive settles it immediately, and where the original is too damaged to read, the absence of a coherent filesystem on the other is itself the answer.
Fifth — physical evidence. A drive somebody has been working on shows it: disturbed screws, tool marks, a broken seal, or a lid that has been off. That also answers a more important question, which is what was done.
Why that matters more than the labelling, and it is worth asking about plainly: "in the process of trying to fix it" covers a wide range. A drive connected to different machines is one thing. A drive opened outside filtered air is another, and if the assembly was opened it should be treated as contaminated from the outset rather than discovered to be later. Nobody is being criticised for having tried — but the bench needs to know.
Why the donor being present is genuinely useful: if a transplant is required, a matching drive is already here. Whether it is suitable is a separate question — heads are calibrated to the drive they were built into, and a donor needs matching firmware revision and usually a narrow manufacture date window. But having a candidate on the bench is a real head start.
On the bench
Both drives were identified from serial, manufacture date and self-reported operating history before any work — an internal log recording powered hours and start counts in a query taking seconds, and two drives of different service lives reporting very different figures. Repair activity was established on each and both examined for evidence of opening, since an assembly opened outside filtered air must be treated as contaminated from the outset. The original was identified by filesystem presence, and the donor retained as a matched parts source.
The outcome
Both drives identified from their own recorded history and content, repair activity established, and the donor retained. Free assessment, one fixed written figure including VAT, 50% of parts and labour upfront with the balance only on successful recovery. The decode: identical drives are not indistinguishable. Each keeps an internal log of powered hours and start counts, readable in seconds, and two drives with different service lives report very different figures. Reading the first portion of each settles it outright — one has a filesystem and the other does not.
Two matching drives and no idea which is which
Send both and don't guess — the drives identify themselves. Each keeps an internal log of how many hours it has been powered and how many times it has been started, readable as a query in seconds, and a drive that lived in a machine for years reports a completely different figure from one bought recently for parts. Manufacture dates differ too, and most conclusively, reading the first portion of each shows which one carries a filesystem. Do say what was attempted while trying to fix it, particularly whether either was opened — that changes how both are handled and nobody will be cross about it. And having the donor already on hand is genuinely useful if a transplant turns out to be needed.
Send both — call Guildford Data Recovery on 01483 901310; each identified from serial, manufacture date and recorded operating history, repair activity established, donor retained as a matched parts source.
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.