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iMac hard drive and Fusion Drive – clicking, slow or doomed

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Quick answer

If your older iMac is clicking, hangs on the Apple logo, or has suddenly become slow, it's almost always the HDD half of the Fusion Drive that's dying. The single best repair is to replace the entire Fusion Drive with a pure SSD — that fixes the issue permanently and makes the iMac 5-10x faster. See current per-model pricing at macmo.dk/reparation.

Why do Fusion Drives fail?

Fusion Drive was a compromise solution: large capacity (1-3 TB) at a price where pure SSDs would have been too expensive in 2012-2017. But that compromise had a cost — the mechanical HDD half is vulnerable to wear:

  • HDD failure after 5-8 years of use — wear on bearings, read/write heads, or magnetic platters
  • Corruption after an uneven shutdown — Fusion Drive is harder to recover than a pure SSD
  • Reduced performance over time — fragmentation on the HDD half

Apple stopped selling Fusion Drive in 2020 (with the iMac 27” 2020), and every new Mac since then has been pure SSD only.

The best repair: replace it with a pure SSD

Instead of swapping the HDD for a new HDD (which will die again in 5-8 years), we almost always recommend an upgrade to a pure SSD:

Benefits:

  • 5-10x faster performance
  • No mechanical parts = far longer lifespan
  • No clicking sounds
  • Silent operation
  • Lower power consumption
  • A permanent fix for the Fusion Drive issues

Pricing including SSD and labour:

  • 1 TB SSD: DKK 2,500-3,500 (21.5”), DKK 3,000-4,000 (27”)
  • 2 TB SSD: DKK 3,500-4,500
  • 4 TB SSD: DKK 5,500-7,000 (only for intensive use)

See the current price for your model at macmo.dk/reparation.

We use Samsung 870 Evo or Crucial MX500 for SATA iMacs, and Apple-compatible NVMe drives for 2017+ models with PCIe SSD. You get 2 years’ warranty and a considerably faster iMac.

Can you rescue my data first?

Yes, in most cases. We have specialist equipment to read data from failing HDDs, and if the SSD half of the Fusion Drive is intact, we can usually rescue everything that lived there. If the HDD is already completely dead, data recovery is added on top of the SSD upgrade — see current pricing at macmo.dk/reparation.

Recommendation: always make a backup before you need one. Time Machine + a 2 TB external SSD is the cheapest insurance you can buy.

How to check whether the Fusion Drive is dying

⏱ PT5M

  1. Listen for clicking. Close all apps. Sit quietly in front of the iMac. If you can hear repeated clicking from the back, the HDD half is dying.
  2. Check Disk Utility. Open Disk Utility (Cmd+Space → 'Disk Utility'). If you see two drives (an SSD and an HDD) instead of one Fusion Drive, the Fusion Drive is 'split' — that indicates a fault.
  3. Check SMART status. In Disk Utility: select the HDD (Macintosh HD or similar), check 'SMART Status'. If it says 'Failing', replace the drive immediately.
  4. Make a backup now. Plug in an external disk and start Time Machine, or upload important files to iCloud. Every hour counts when an HDD is clicking.
  5. Book the repair. Bring the iMac to us, or send it in. We can usually replace the SSD and rescue the data the same day.

Frequently asked questions

What is a Fusion Drive?
Fusion Drive was Apple's hybrid solution from 2012-2020: a small SSD (24-128 GB) combined with a large HDD (1-3 TB), automatically managed by macOS. macOS placed frequently used files on the SSD and the rest on the HDD, giving you both speed and capacity. The problem: when one of the two drives fails, the whole Fusion Drive fails — and the HDD half was the most common point of failure.
My iMac is clicking — what do I do?
STOP using the iMac immediately. The clicking sound is the HDD half in the process of dying. Every minute from now on reduces the chance of saving your data. Make a backup if possible, or bring it to us straight away. We can usually rescue the data and replace it with a pure SSD in the same job — typically DKK 3,500-5,500 in total. See the current price for your model at macmo.dk/reparation.
What does it cost to replace a Fusion Drive with a pure SSD?
Between DKK 2,500 and DKK 4,500 depending on model and SSD capacity — DKK 2,500-3,500 for the iMac 21.5'' with a 1 TB SSD, DKK 3,000-4,000 for the iMac 27'' with a 1 TB SSD, plus DKK 800-1,500 extra for a 2 TB SSD. The 21.5'' is slightly more expensive than the 27'' because disassembly is harder. See the current price for your model at macmo.dk/reparation. Includes labour and 2 years' warranty.
How much faster will the iMac be with a pure SSD?
5-10x faster on real everyday tasks. Boot time from 60 seconds to 15 seconds. App launches from 5-10 seconds to under 1 second. File transfers 5-10x faster. It's the single best upgrade you can make on an older iMac.
Should I choose an SSD or a new iMac?
If your current iMac is from 2017+, runs Sonoma or Sequoia, and has 16 GB+ RAM: repair with an SSD upgrade (DKK 2,500-4,500). You save DKK 6,000-12,000 versus a new M4 and get a fully working computer for another 3-5 years. If the iMac is from 2014 or earlier and only has 8 GB RAM: a new iMac is the better buy. See current SSD upgrade pricing at macmo.dk/reparation.