Late 2015 27" iMac [17,1]. Fusion to SSD. Separate Fusion?

[MrMJS]

Hello.

The HDD inside my model 17,1 iMac is a 3Tb Fusion Drive. I removed the HDD and added a 1.0TB OWC 6G SSD.

Before swapping the drives I used Carbon Copy Cloner to clone the HDD to the SSD.

The 128gb Apple SSD is still inside the iMac.

I did not split the drives before switching out the HDD for the SSD. Should I have slit the Fusion Drive before replacing it? is the system still considering this to be a Fusion set up? Or am I misunderstanding how a "Fusion Drive" works?

 

[glenthompson]

If you didn’t split the fusion drive is is still working as a fusion. I would recommend splitting it and reclaiming the space.

 

[MrMJS]

In hindsight, I probably should have set this up to boot from an external SSD via Thunderbolt 2, split the Fusion Drive, use the internal SSD as a backup bootable, and the HHD for data. This is still an option as I haven't "taped" the screen yet.

Is it best to do a clean install and start from scratch?

 

[Tricone]

I am basically in the same boat. I'm confused by what this "splitting" means. I was considering upgrading my 3TB internal Fusion Drive to an internal SSD, and was hoping that I would not have to utilize the internal 128GB Apple SSD whatsoever. I'd like to install the OS on the new SSD, install it internally, then boot entirely from said new SSD. However, it would be nice to utilized CCC, and clone the Fusion Drive over to the SSD before installing it internally. If I do so, would the Mac boot from the new SSD, or would I have to first erase/format the Apple 128GB SSD?

Hello.

The HDD inside my model 17,1 iMac is a 3Tb Fusion Drive. I removed the HDD and added a 1.0TB OWC 6G SSD.

Before swapping the drives I used Carbon Copy Cloner to clone the HDD to the SSD.

The 128gb Apple SSD is still inside the iMac.

I did not split the drives before switching out the HDD for the SSD. Should I have slit the Fusion Drive before replacing it? is the system still considering this to be a Fusion set up? Or am I misunderstanding how a "Fusion Drive" works?

 

[glenthompson]

I am basically in the same boat. I'm confused by what this "splitting" means. I was considering upgrading my 3TB internal Fusion Drive to an internal SSD, and was hoping that I would not have to utilize the internal 128GB Apple SSD whatsoever. I'd like to install the OS on the new SSD, install it internally, then boot entirely from said new SSD. However, it would be nice to utilized CCC, and clone the Fusion Drive over to the SSD before installing it internally. If I do so, would the Mac boot from the new SSD, or would I have to first erase/format the Apple 128GB SSD?

Splitting means to break apart the two drives into individual drives and formatting them as separate drives. Yes, you will need to reformat the SSD in the process. In your proposed case I would clone the existing drive to the new SSD in an external enclosure. Verify that it boots. Split the Fusion drive then install the SSD. Boot into the new SSD and format the 128 gb drive for whatever you want it for. Keep your old spinning drive as a backup.

 

[corsaro]

Hallo all, reading these posts I’m afraid there is a wrong expectation: if you upgrade your fusion drive with an SSD, you will not leverage it at full speed, because the channel used to connect to the motherboard is much slower than the channel used by the internal SSD of the fusion drive. Thus the original SSD of the fusion drive will be faster, even if you change the hard disk with a very fast SSD model, you just don’t use it at full speed. i didn’t make any test, but I suspect an external thunderbolt drive could be even faster.