I want to completely stop my internal Fusion drive from powering up, since I no longer use it and it is very noisy.

My late 2012 27” iMac came with a Fusion drive, which has long since stopped working correctly. In fact, I long ago began using an external Thunderbolt drive for macOS and documents; now using Mojave 10.14.6.

I no longer use the internal drive(s). I also disassociated the two parts of the Fusion drive and reformatted them as 2 separate drives, one becoming a 120GB SSD, and the other a larger hard disk drive. The Fusion drive is labeled as follows: “Type: SATA Internal Physical Volume” “Device: disk1s2”. The SSD part of the disk still usually mounts. The SATA hard drive only mounts occasionally at start-up, and often dismounts itself after unsuccessfully getting stuck reading. (It will show up for a while sometimes and start to show the hierarchy, before shutting down.)

I prefer not to physically open the iMac to remove the drive (apparently, it's not a simple operation).

My big problem is the noise from the internal disk trying to spin.

I would like to completely disable the internal Fusion drive. I see some suggestions online from many years ago, and many previous versions of macOS, using Terminal commands, but am unsure if they would still work, and I don’t have much experience.

Suggestions? (This Mac has run 24 hours a day since 2012. I’m not tossing it. It still works great.)

  • In the same situation I just removed any partition from the HDD but kept the gpt table. "I see some suggestions online from many years ago, ..." - please add some links. – klanomath Apr 15 at 9:29
  • klanomath >>> www.google.com/search?client=firefox-b-d&q=mac+how+to+turn+off+an+internal+hard+drive – libertedepense Apr 15 at 9:56
  • @libertedepense I simply removed all partitions: diskutil list to get the device/partition identifier(s) of the internal HDD (usually disk1 & disk1s1 - disk1s3), unmounted all volumes: diskutil umount disk1s2. Removed all partitions: sudo gpt remove -i 2 disk1, sudo gpt remove -i 3 disk1, sudo gpt remove -i 1 disk1 and finally sudo pmset -c disksleep 1. – klanomath Apr 15 at 10:14

I want to completely stop my internal fusion drive from powering up, since I no longer use it and it is very noisy.

You cannot prevent your mechanical drive from powering up.

It’s a standard 3.5” SATA hard drive with a power connector directly connected to the power supply. There’s no switch or command you can issue that will cut off the power to the drive. Repartitioning it and wiping it clean won’t prevent it from spinning up and doing its periodic reads.

iMac SATA Drive

The only solution is to disconnect it.

However, since you have to go through the trouble of cutting through the adhesive holding the glass, you might as well upgrade the drive to an SSD. I’ve done this exact procedure - it’s not difficult, just time consuming.

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