How can I partition a Fusion Drive on an iMac to install Zorin?

I'm in the process of installing Zorin 17 and have reached the point of partitioning the Fusion Drive on my iMac, which consists of an SSD and a traditional HD. On the same computer, I'm using macOS and cannot format it.

I've searched online for guidance in such cases and have also attempted to create a partition using macOS Disk Utility, unfortunately without success. This is because I can only partition the SSD, which has limited available space.

One potential solution would be to separate the two disks using the macOS Terminal, but that would involve formatting the entire system.

I'm asking if anyone has encountered this situation before and how I can proceed to partition the Fusion Drive.

Thank you very much.

Perhaps the solution is to use only the SSD for the operating system and use the hard drive portion for the Home folder? I think those hybrid drives are supposed to be smart in that they figure out where to put things but not sure if they have their own firmware or if the Apple software did some of the heavy lifting to move things around. If it is possible to put the Home folder on the HDD, that is what I would do. That way the operating system is on the SSD in order for fast access/execution and working files are in the larger but HDD. Let us know what you find out because I am curious how that would work.

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Hi Makaru,

I do not currently own a Mac with a Fusion drive. My main Mac is a 2019 27-inch iMac (1TB SSD), and a 2020 MacBook Air.
On the other hand, I have owned many Macs over the decades and have done a lot of software/hardware tech work inside these and other Macs.

Some of your situation may depend on several things:
Specific Macintosh Model (iMac, Mac Mini, MacBook, etc)
Year of the Mac release
Internal Drive storage capacity selected when Mac purchased (1, 2 or 3 TB HDD)
Mac OS version you are running.
(See the Fusion models chart list I paste in below.)

My suggestion is to instead consider creating an external SSD to install ZorinOS onto, and then choose to boot from that at Mac startup time.
I have done this sort of thing with many many various versions/releases of the MacOS itself, as well as with a variety of Mac 'Tool' drives (both commercial and home-made). And assuming you are using either Firewire (on older USB 2 only Macs) or USB 3 on newer Macs, the boot and run process can be quite snappy and respectable with booting from a fast SSD.

But if you are determined to explore the partitioning of Fusion anyway ...
If Disk Utility (the GUI) program allows you to partition the drive, say when booted from Safe mode or from other root level repair/access, then that might be OK, because it will be the MacOS itself knowing about the Fusion drive and how to handle such a split.

I would NOT EVER try to boot from a GPartEd live drive and use it to resize a Fusion drive, because MacOS would be having no knowledge of that process, and data could be lost since parts of some files may reside on both the HDD and the SSD components. Worst case -- it could totally corrupt the Fusion drive and force you to re-format and reinstall everything from a backup. You did make a backup first, right?

Note 1: The fusion drive will look like one single drive to the MacOS. With its size being the sum of the two components. The Mac utilities will not show you the two drive components separately. (Terminal: diskutil list will reveal a single device, say of 1.12 TB or 1.03 TB.)

Note 2: The SSD portion of a Fusion drive may be soldered to the Mobo and not otherwise accessible nor upgradeable. (depends on the model, etc.)

Note 3: The Fusion data movement process is managed by the MacOS at a very low data block-level. There is no reliably user-accessible way of knowing which of the two components actually has a particular file or chunk of a file.

Note 4: It is NOT like a traditional HDD cache which mirrors and moves the data between the two. Though the Mac OS does typically allocate 4 GB (or more) to the function of data buffering when reading writing data in and out of the Fusion Drive.

Note 5: The Mac OS monitors the files usage, and stores the most commonly used (important/essential) data on the SSD. This is typically the Mac Operating System programs and files and likely the most used application programs.

Note 6: Research shows that in some cases, it may only store a PART of an often used large file on the SSD, with the rest of the large file being on the HDD. This can happen because the fusion drive operates on a data-block level, not file-object level.

Note 7: Do not format a physical spinning platter disk HDD with Apple APFS format (if one can avoid doing so). The performance of APFS on spinning HDD is HORRIBLE. Try to keep those at HFS+/MacOS Extended. APFS is designed for Solid State technology drives.


Mac Models with Fusion Hybrid drives:
2012-mid 2015 Macs : HDD 1, 2 or 3 TB + 128 GB SSD
Late 2015-2020 Macs: HDD 1 TB + 24 or 32 GB SSD (no longer offers 128 GB)
Late 2015-2020 Macs: HDD 2 or 3 TB + 128 GB SSD
Dec 31, 2019

NOV 12, 2012

May 30, 2013

October 24, 2012


After days of searching and testing, I figured out that the only way I have to install Zorin is on an external SSD and boot it from it.
Unfortunately, because I cannot stop to work on my mac and it is my main computer either, I cannot format, partition or separate my Fusion Drive.

Thank you for your replies, helped me a lot!
I hope someone else can find another solution for their needs.

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