Data Recovery Case File · Formatted & Logical Faults · The Table Is Partly Intact
Two Partitions, One Gone: What That Localises
His enquiry was two lines and contained a nearly complete diagnosis. A LaCie 2TB external drive: "it has 2 partitions within its 2 terabyte capacity. I can see 1 partition but the other is missing." That asymmetry is the whole story. A drive with a serious fault does not present one working volume and lose another — it fails wholesale. One partition working and one missing means almost everything is functioning, and the failure is confined to a single record a few hundred bytes long. It is among the most recoverable situations in this archive, with one specific way to ruin it.
| Media | LaCie 2TB external hard drive carrying two partitions — one mounting and accessible, the other absent from the system |
| Reported situation | Drive powering, spinning and enumerating normally · first partition mounting and usable · second partition not presented · no fault reported with the working volume |
| Fault class | Partition table entry damage — single entry lost or corrupted while the remainder of the table and the drive itself function normally |
| Equipment used | Imaged write-blocked before any repair · partition table examined and the missing entry reconstructed from the volume's own boot records on the image · filesystem verified from the copy · contents delivered |
The decode: what one working partition proves, and the button that loses both
How a drive describes its partitions: near the start of the disk sits a small structure — the partition table — listing each partition's start, size and type. It is tiny, and it is the only place that description exists. Everything else on the disk is the partitions themselves.
What his symptom proves: a great deal. For one partition to mount normally, the drive must have powered, spun up, identified itself, reported its capacity, and had its partition table read successfully enough for the system to find and mount that volume. So power, mechanism, electronics, interface and most of the table are all confirmed working by the partition he can see. What has failed is one entry in that table, or the boot record of the second volume — a few hundred bytes describing where the missing partition begins and how large it is. The data in that partition is entirely untouched; nothing currently tells the computer it is there.
Why that is so recoverable: because filesystems keep backup copies of their own key structures at known positions inside the volume, precisely for this. Scanning the disk finds the missing volume's own boot record, which states its size and layout, and from that the partition entry is reconstructed exactly. The result is the volume returning with its folder tree, filenames and dates as they were — not a carve.
The button that loses both: and this is the specific danger of a partly-working disk. Because one partition mounts, the drive looks alive and repairable, so people run disk repair utilities against it or accept an offer to fix the disk. Those tools rewrite the partition table. A rewrite that does not correctly identify the missing partition can produce a table describing only the visible one — making the loss permanent by removing the traces a reconstruction reads. The other common mistake is creating a new partition in the apparently free space, which writes a fresh empty filesystem over the missing one. Neither should happen.
What to do meanwhile: stop using the working partition too. Writing to the disk risks landing in space the system believes is unallocated — which is precisely where the missing partition lives.
On the bench
The drive was imaged write-blocked before any repair was attempted, so that everything happened against a copy and no utility could rewrite the table on the original. On the image the partition table was examined and the surviving entry compared against the disk's actual layout, then the missing volume's own boot record was located within the unallocated span — filesystems maintaining backup copies at known offsets for exactly this purpose — and the partition entry reconstructed from it precisely. The filesystem was verified from the copy, mounting with its folder tree, filenames and dates intact, and the contents delivered on fresh media.
The outcome
The missing entry reconstructed from the volume's own records and the partition returned intact. Free assessment, one fixed written figure including VAT, no recovery, no fee. The decode, for anyone with one partition working and another missing: the working one proves power, mechanism, electronics and most of the partition table are all fine, which localises the fault to a few hundred bytes describing where the missing volume starts; the data in it is entirely untouched and nothing currently points at it; filesystems keep backup copies of their own boot records inside the volume, so the entry can usually be rebuilt exactly rather than carved; and the danger is that a partly-working disk looks repairable — so run no repair utilities, accept no offers to fix the disk, and never create a new partition in the free space.
One partition visible and one missing
Don't try to fix the disk, and don't create anything in the empty space. The partition you can still see is proving that your drive, its electronics and most of its partition table are all working — which means the fault is confined to one small record describing where the other volume begins, and the data in that volume is completely intact. It just isn't being pointed at. The risk is that a partly-working drive looks repairable, so people run disk repair tools or accept an offer to fix it, and those rewrite the partition table; a rewrite that doesn't correctly find the missing volume makes the loss permanent by removing the traces a reconstruction reads. Creating a new partition in the unallocated space is worse still, because it writes an empty filesystem straight over the missing one. Stop writing to the working partition too.
Don't let anything repair it — call Glasgow Data Recovery on 0141 404 0294; imaged write-blocked, the missing entry rebuilt from the volume's own records, folders and dates returned intact.
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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.