Frozen at the Apple logo, cycling round and round. Recovery Mode falling over. Disk Utility powerless to repair it. A failed macOS update is seldom a dead drive — it’s a wrecked file system on a disk that had quietly started to fail.
← All case files · £300 + VAT flat · Fusion £550 + VAT flat
Switched on, the iMac climbed as far as the Apple logo and then went round in circles. It would reach for the built-in recovery routine, fall over, and try again; Disk Utility, launched from Recovery Mode, refused to repair the volume. There was no Time Machine backup to fall back on.
When a drive fails partway through an update, luck rarely has much to do with it. A macOS upgrade rewrites an enormous amount of file-system housekeeping in one concentrated burst, and a disk whose sectors are close to spent will handle light everyday use for months before that sudden demand finds them out. The update didn’t wear the drive down — it was simply the first job to call on the whole disk at once.
the direct reason the machine wouldn’t boot.
with SMART reporting genuine, measurable wear.
An Intel iMac stores its data on a removable SATA disk or SSD, and that’s the uncomplicated case — a flat £300 + VAT.
A Fusion Drive iMac is another matter. It pairs an SSD with a spinning disk and presents the two to you as one volume, so the instant either half drops out, the entire volume vanishes — which is precisely the corner a Fusion machine is backed into at a moment like this. Both halves have to be recovered and the single volume rebuilt from the pair: £550 + VAT, flat, with both drives sent in together.
Where the storage is soldered on — the T2 and Apple Silicon iMacs — we decline the job outright. The flash is fixed to the logic board and locked to the Secure Enclave, so there is genuinely nothing on it we could hand back, and we would far rather say so at the door than charge you to arrive at the same answer.
With a failing disk in front of us, none of the work happened on the Mac. We imaged the drive slowly on a DeepSpar, lifting the sound regions first and drawing the weak sectors out over several measured passes, a PC3000 on hand for any firmware trouble — and everything after that was done against the clone. From the image we set the broken APFS structures back in order, reassembled the file system and pulled the data out. The original was read and never written.
Rebuilt from the clone, the file system came back whole, folder hierarchy and all.
On an update failure the result hangs almost entirely on what happens between the crash and the disk arriving with us. Powered down at once and brought straight in, an iMac is usually a clean job. Put through two weeks of restarts, First Aid runs and repeated update attempts, its already-weak disk has been read close to exhaustion — and some of what it held will not return.
When a Mac stalls after an update, the urge is to keep trying things. Each of those things is a gamble, and the harm they do climbs in roughly this order:
every cycle sweeps the heads across a surface that is already breaking down.
it writes into the file system; a repair it can’t make on the first attempt it won’t make on the fifth.
the move that ends it — a reinstall overwrites file-system metadata, and on APFS that is exactly the map a recovery would otherwise trace back along.
Switch it off and leave it off. That is the whole of the advice, and it is free.
Drop the drive at our Guildford Business Park reception, or post it to us — it costs nothing to find out what happened. You get a written figure from the fixed bands before any work begins.