Data Recovery Case File · Desktop Externals · The Three Tenants

Partitions aren't separate drives: a three-volume 4TB's slow-motion decline decoded — and every tenant, photo collection first, moved out in time

His enquiry described a household in slow collapse. The LaCie Porsche Design 4TB is "partitioned into three individual drives" — 1.5TB, 1TB, 1.5TB — and boot-time had become a queue: "two drives are recognised in around five minutes, but one drive — which I think is the main problem — can take ten to fifteen minutes." Folders and files load slowly everywhere; nothing can be copied or saved; and the slowest tenant arrives with a warning attached: "macOS cannot repair the disc 'Photo Collection.' You can still open or copy the files, but you can't save changes." His instinct — that the slow one is the main problem — was half right in an important way: the problem lives under all three, and the page below retires the most consequential misunderstanding in home storage: that partitions are separate drives with separate fates.

The decode: three tenants, one building — and what the fifteen-minute mount was counting

The misunderstanding, retired first: partitioning divides a drive's address space, not its hardware — three volumes on one 4TB share the same platters, the same heads, the same motor: three tenants in one building, with separate front doors and a single foundation. When the foundation moves, every tenant feels it — which is exactly his picture: universal slowness across all three volumes (the shared mechanism labouring), with the worst symptoms concentrated where the building's subsidence happens to run (the photo volume sitting over the most-degraded territory, hence its fifteen-minute arrivals and its repair refusal). "The main problem" wasn't that partition; it was the ground under it — and the practical consequence cuts hard: a failing partition on a shared drive means every partition is on deadline, including the two that still feel healthy. The minutes, given their true name: this archive retires the fullness myth wherever it appears — mounting that stretches toward quarter-hours is retry saturation, a declining mechanism re-asking failing reads until they land, the delay growing as the decline deepens. Five minutes was already the warning; fifteen was the warning shouting. And the macOS message, decoded as the protection it is: "cannot repair... you can still open or copy, but you can't save changes" is the system finding the photo volume's structures damaged, declining to write corrections it can't trust to hold, and mounting read-only — deliberately preserving what remains by refusing all writes, his failed saves included. It is the operating-system version of this archive's own doctrine: when the ground is failing, stop writing on it. The window it was protecting — open-and-copy, while the reads still eventually land — is precisely the window the recovery below used.

The recovery — the building imaged, all three tenants rehoused

The bench treated the patient the partitions share: the drive assessed on its native interface, its media decline confirmed and its mechanism supported with donor attention, then the whole 4TB imaged once under management — the healthy expanse banked at pace, the subsided territory under the photo volume negotiated last in bounded, retry-governed passes, coverage closing in the high ninety-nines. From the image, each tenant was rebuilt and verified in turn: the two quicker volumes mounting whole; the photo collection — the read-only warning's ward — reconstructed with its damaged structures repaired on the copy, its library opening picture by picture across the set, the bounded losses at the worst territory itemised by folder. All three went home organised on new media in duplicate, one healthy building for three tenants — with the delivery note's structural line earned three times over: partitions organise a drive; they do not diversify it — three volumes on one mechanism is one copy wearing three names, and the second building is the only protection any tenant ever really has.

Outcome

All three volumes recovered, the photo collection intact behind its protective warning — and the partition filings every multi-volume drive owner needs. One slow partition condemns the building: shared hardware means shared fate — copy everything off the day any volume starts crawling, not just the noisy one. Read repair-refusals and read-only mounts as gifts: the system is preserving your open-and-copy window by refusing writes — use the window for copying, never for one more repair attempt. And retire the minutes myth for good: mounting measured in minutes is failure in progress, whatever the drive's fullness. His building gave three warnings at three speeds. Every tenant got out — and now lives, as tenants should, in more than one place.

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.