stop 2012 iMac internal fusion drive from powering up

[libertedepense]

stop 2012 iMac internal fusion drive from powering up

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 the OS & documents. 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 120 Gb SSD, and the other a larger classical 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 traditional part of the drive only mounts occasionally at start-up, and often unmounts 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 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 OSs ago, using terminal, but am unsure if they would still work, and don’t have much experience with terminal.

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

 

[tyc0746]

I suppose if the machine is never put into sleep/hibernation you could just unmount it so the system doesn't try to keep accessing it.

Otherwise you'll have to remove power from it in some manner - which will involve physically opening the iMac.

 

[libertedepense]

Thanks tyc0746. It doesn't appear to work. That doesn't seem to cut the power. I'm speculating. It seems to operate just like an external disk being plugged in again – doesn't matter if it was unmounted previously.

 

[tyc0746]

Sounds like it's auto mounting each time - if I unmount an external drive and don't unplug/replug it then it doesn't re-mount automatically, so it must be something specific to internal drives.

There are terminal commends to disable this, but I've never tried them myself...

Prevent a volume from mounting at startup - Apple Community

discussions.apple.com

Don't know if that would stop it powering up at all though, or just stop it mounting to the desktop.

The other option noted at the bottom of that link would be to encrypt the drive and not enter the password - so it can't mount.

 

[Fishrrman]

Can you erase the internal HDD using disk utility?

If so, I'd suggest this:
1. Use disk utility to erase the internal HDD. Just leave it "erased, but empty".
2. Get ahold of the "Semulov" menu bar utility (it's free):

kainjow

3. Launch Semulov. Use it to "dismount" the internal HDD
4. Hopefully this will eject the drive from the desktop and "spin it down" at the same time.

If the Mac (for whatever reason) tries to wake up and re-mount the drive, you should be able to use Semulov to just eject it again.

I REALIZE this is not "the full solution" to your problem.
But it could serve as a usable "workaround".

I believe there may be a way to set up the OS to automatically dismount the drive at boot, using a script or something along that line, but I've never tried it.

 

[libertedepense]

Can you erase the internal HDD using disk utility?

Nice idea, but I'm pretty sure I've tried to reformat & it doesn't get as far as erasing...
Thanks for the Semulov, sounds like a gimmick I might like.