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MHDR / Specialist cases / iMac Fusion Drive recovery

Specialist · iMac Fusion Drive recovery

iMac Fusion Drive recovery, Maidenhead. One volume, two drives, and the noisy half decides the job.

Fusion iMacs reach us from Maidenhead and the towns around it with much the same account: a machine that has grown slower across a season, then a grinding note from behind the screen. Apple pairs a small SSD with a 3.5-inch hard disk and presents the two as a single volume, so the mechanical half takes the whole volume down with it when it goes. Add a display bonded shut, and on newer machines encryption held in the controller. Ring before posting anything from Maidenhead and an engineer will say which way to send it.

No fee unless the data comes back Diagnosis free, then a fixed quote Post it in from Windsor, Slough or anywhere else

Describe the fault to an engineer
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What each Fusion Drive symptom is telling you.

None of these? Run the triage →
The symptomThe likely causeStart here
A grinding note from behind the screenThe 3.5-inch half of the Fusion pair is failing mechanicallyPower it down and leave it
Question mark folder at bootThe volume will not mount: one member of the pair has dropped out of itStop there; do not reinstall
The iMac was knocked over while onHeads parked badly against moving platters, though the surfaces often surviveRecoverable as a rule
Everything opens, but each file takes a minuteSectors are being re-read until the disk gives up on them altogetherTake an image while it reads
Disk Utility offers to erase and rebuildRebuilding writes a new map over the one that still describes your filesDecline it; the map is the data
A T2 or Apple-silicon iMac with no passwordEncrypted at the controller, and the key answers only to that passwordFind the password or recovery key
If you post it in: use a tracked, insured service addressed to our secure intake lab, and the return leg is paid at our end; if you would rather check the packing first, an engineer will go through it by phone. Each step is set out on the postage page.

What is inside a Fusion iMac, and what fails.

Fusion DriveOne logical volume laid over two devices: a small SSD — 128GB on the 2012 machines, cut to 24 or 32GB later — and a hard disk of one to three terabytes. macOS keeps what you use most on the fast half and moves the rest across quietly.
The iMac and Mac miniiMacs from 2012 to 2019, Mac minis from 2012 to 2014. In an iMac the 3.5-inch disk and the blade SSD sit behind a display bonded on with adhesive; a Mac mini pairs a 2.5-inch disk with a blade under its base plate. Once both are out of the case they are ordinary drives on a bench.
The mechanical halfWhere the trouble almost always starts: noise, long pauses, sectors that will not read. It goes first, and it decides how the job runs.
T2, FileVault and Disk UtilityThree limits worth knowing before you begin. First Aid repairs a file system; it recovers nothing. FileVault without the password is a closed door. And on a T2 or Apple-silicon machine the key is sealed in the controller, so a dead logic board can end the matter.

What happens between arrival and return.

The most recent cases →
01

Booked in, then assessed at no cost Free

Nothing becomes chargeable until you have said yes to it. Each item takes a case number of its own the moment it arrives, an engineer establishes what has actually failed, and you are given a candid view of which files stand a realistic chance of returning. The single quote that follows is fixed, written down, and costs nothing.

Diagnosis at no costOne fixed quote, in writingNothing signed
02

The display off, both drives out

An iMac is opened before anything else can happen: the adhesive holding the display is released, the panel lifted on its cables and set aside, so that the SSD and the hard disk behind it can be labelled and taken out as a pair.

Display and panel lifted clearThe precise fault located
03

Image each half in turn

Both members are imaged before a single decision is taken about the volume. The SSD copies in minutes; the mechanical half is read in short passes on a bench rig, its awkward zones deferred to the end, and neither original is ever written to.

Each half imaged firstThe originals left untouched
04

Rebuild the Fusion mapping

The map of which blocks sit on which member belongs to CoreStorage on the earlier machines and to APFS after that. It is rebuilt against the two images, and the files that come off them are complete.

The CoreStorage map rebuiltWhole files, not fragments
05

Opened, verified, and sent home

Nothing is billed until you have seen the recovered file list in full and told us to go ahead. What comes back arrives on new media, with the return journey at our cost, and the case stays open at this end until you have opened every file yourself.

You approve the list firstReturned on fresh mediaThe return post is ours

What tends to show up first

  • One volume, two devices — the SSD and the hard disk only mean anything together, since a single file may begin on one and finish on the other. Both come to the lab, each labelled with which half it is.
  • The display is glued, not screwed — from 2012 the panel is held by adhesive strips and its cables are short, so it is parted from the frame with a thin wheel and lifted slowly. That is the first job on the bench, before any recovery begins.
  • Noise sets the clock — a knock or a grind from the 3.5-inch half is mechanical damage, and macOS answers a failing disk by retrying the same region until it stalls. Each further boot spends reads the imaging pass will want.
  • A T2 or Apple-silicon iMac is another machine entirely — the controller encrypts as it writes and keeps the key to itself, so the password or the recovery key is the whole job. Without either, the NAND is unreadable by anyone.

Why an iMac tends to arrive holding the only copy: it sits on a desk for eight or ten years, gathering everything a household or a studio makes in that time, and because Fusion presents itself as one quick volume most owners never register that a spinning disk is in there at all. Two endings account for most of what we see. The mechanical half wears out and announces itself — noise first, then long pauses, then a volume that will not mount. Or a newer machine shuts itself behind a controller that will not surrender its key. The first is bench work; the second turns on a password. Describe the noise and we will say which you have.

From the casebook, lately.

MH · MHD-2026-6841ON RECORD ✓

The iMac that was still in use, a fortnight into the noise

It had been grinding for a fortnight and was still being worked on daily, which is the part that costs most. The display came off, both members of the pair were labelled and lifted out, and the noisy 3.5-inch disk was imaged over several sittings, the easy zones taken first, before the SSD was copied in a few minutes. The CoreStorage map was rebuilt across the two images and every file came off whole. Three days from arrival.

100% imaged3 days from arrival

Before the iMac comes to the lab.

Do these now

  • Send both drives, each labelled with which half it is
  • Send the login password, and the recovery key if set
  • Leave the machine switched off
  • Tell us the model year of the iMac

Things best not done

  • Booting it again to hear how bad the noise is
  • Letting Disk Utility erase or rebuild
  • Reinstalling macOS over the failing volume
  • Levering the display off without tools

The questions that arise most often.

My iMac has begun grinding — can I keep working on it?

Grinding or a rhythmic knock comes from the 3.5-inch disk that forms half of the Fusion pair, and it means the mechanism itself is damaged rather than the software above it. The slowness you have noticed has the same root: a read that fails is attempted over and over before the system moves on from it. Every further boot spends reads you may want later, so shut it down at the wall and leave it off until an engineer has seen it.

Only the hard-disk half has failed. Is my data still there?

Very likely, though not from that half on its own. Apple lays one logical volume — CoreStorage on the older machines, APFS on the later ones — across a small SSD and a hard disk, and the map recording which blocks live where is spread over both. A document can begin on the SSD and finish on the disk, so reading the surviving member alone returns fragments with no filenames worth having. The work is to image both members, then rebuild that map against the two images.

Do I have to take the display off to reach the drives?

That is the part of an iMac people underestimate. From 2012 the display is held on with adhesive strips rather than screws, so those strips have to be cut through, the panel lifted while its cables are still attached, and fresh adhesive fitted on the way back; both drives sit behind the panel itself. If you would rather not attempt it, say so when you ring and an engineer will go through the options before anything is posted.

My iMac has a T2 chip and the password is lost. Now what?

Then, honestly, there is nothing anybody can recover. On an iMac carrying a T2 chip, and on every Apple-silicon machine, the storage is encrypted by the controller as it is written, and the key that undoes it stays inside that silicon, released only against your password or recovery key. No laboratory in Britain can read the NAND without one. Fusion iMacs from before 2018 are a different matter, provided FileVault was never switched on.

More of the jobs we've closed.

Fitted drives → Noisy drives → No drive detected → Media we work with →

Switched off, it keeps every chance it has.

Each further power-up asks more of a drive that has already begun to fail. Open the case first and let the free diagnosis tell you what is left.

0800 6890668

Ask for a free diagnosis Posting it to us