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Model A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 or 3.5 GHz Core i7 Processor, ID iMac14,2

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How do I split Fusion drive on Mojave / APFS?

Hello.

I have a 2013 iMac that has a Fusion drive. I want to replace its internal HDD with an SSD. My understanding is that I should split the Fusion drive before performing this.

I referred to the article https://www.macworld.com/article/2015664... which discusses the use of diskUtil and Core Storage to get the GUIDs and split the drive.

However, invoking disktutil coreStorage list returned ‘No CoreStorage logical volume groups found’. I then tried diskutil list, which returned more information, apparently showing the fused drives as ‘synthesized’. I read a bit about this in other discussions, and it seems like this is perhaps a Mojave/APFS version of a Core Storage Fusion config.

I’m wondering what I need to do to split my Fusion drive. Is there something else to use, or do I not even need to split the HDD/SSD before replacing the HDD?

Thanks.

-Allan

Update (12/22/2018)

I wonder if I need to downgrade it to High Sierra, and setup the drive as HFS?

Answered! View the answer I have this problem too

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I’m having this same problem and haven’t found resolution. The system fully shows the Fusion drive as one disk, so I have no way to erase each sub-disk separately in order to split it. Any further advice from any would be greatly appreciated.

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I upgraded my Mac Mini 2012 to MacOS Catalina. Then found my two separate drives (SSD and Regular HDD) fused together by the installer.

I wanted to separate them.

Solution below helped me.

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5 Answers

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I did this earlier today on an iMac. Boot to a Mojave USB boot installer. Then Utilities —> Terminal. The commands are along the lines of:

diskutil apfs list

Then make note of the “virtual disk” that is the “Fusion Drive”. This is made up the PCI Flash and the other spinning drive. You can see how the text output of the drive structure is hierarchical.

Let’s say that virtual container disk is identified as “disk0”

diskutil apfs deletecontainer disk0

This command will split your fusion drive, and leave you with two new drives to format via Disk Utility (which you can run in the same USB Booted environment you’re already in).

Format them (the SSD and the other drive) as whatever you want.

I recently did this prior to replacing the slow spinning disk that comprised the 1TB of my Fusion Drive. Replaced that with a 500GB SSD which is SATA3. Installed Mojave onto the 128GB PCI “Blade” Flash and formatted the other SSD.

I then store User home folder on the larger SSD, and macOS and other apps run off the faster PCI-based SSD.

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With this tip, I shared my fusion drive. It's the right decision. thank you!

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THANK YOU!! I knew someone will know how to do this.

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Hi, I don't see it saying "virtual disk" anywhere, however I do see "APFS Container Reference: disk2 (Fusion)" directly under "Container disk2". Is that the one I am supposed to delete?

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@Professional Amateur - yes, that is the one

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Thank you. This tip helped me a ton. I was running Catalina . I did not have to use USB installer. Restarted with Command +R pressed then when the setup menu popped up I opened a terminal window on top left corner.

Typed “diskutil apfs list” then found the disk label. Mine was “disk02s” then

typed “diskutil apfs deletecontainer disk02s”.

It deleted that drive and then went back to the menu and found two drives.

Formatted and reinstalled the Mac OS from the menu.

To my surprise, it was Catalina which was reinstalled.

My Machine is - Mac Mini late 2012 -

To be in the safer side, I formatted my SSD in APFS and other drive in MacOS extended to prevent it fusing together again during the installation.

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Sadly, Apple has not updated the Core Storage section on the developers web site with Fusion Drive running with Mojave. The Man page doesn't offer any help either.

Yes, you do need to break the Fusion Drive set before altering things otherwise the drives will be confused. In this case you also need to keep in mind you can't run the system with a dual SSD Fusion Drive set it won't really make things faster.

I haven't played with Mojave Fusion Drive setup yet my self so I don't know if Apple has any magic behind the scenes.

FYI - Mojave APFS is different from High Sierra APFS so I doubt down grading would work.

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Hi,

I did a similar thing with a Mac Mini. I simply took a time machine backup and then booted to internet recovery. From there I formated each drive in disk utility separatly to break fusion. I then swapped over to the SSD. Worked fine. I hope this makes sense.

Thanks,

Tom.

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(Per Max’s NOV 2019 updated comment regarding not having to split the drives before replacing the HDD — posted in Answers so my post was more visible):

————————————————————————————————————————————————————————————

So for a late 2014 27" iMac with a 1 TB HDD and 128 GB blade (currently running Mojave), I DO NOT NEED TO SPLIT the fusion drive before I replace the HDD with an SSD?

I am planning on formatting the new 2 TB SSD in AFPS format before I install it... and was hoping to fuse the drives because my blade is not large enough as the boot drive (with all the apps I currently have installed — currently as a fusion drive, I only have a few hundred MB of space left on my blade). I read on the comments section for the 2014 replacement kit (on ifixit) that someone successfully fused their SATA SSD with a blade (with both SSDs formatted APFS). I was hoping to fuse the SSDs after replacement to make sure I have sufficient space for all my apps — it's not in the budget to buy a new larger blade, besides the fact I was a little worried about replacing the blade successfully.

Can anyone tell me if I will be able to fuse two SSDs in Mojave or Catalina? If not, how would I make the SATA SSD my boot drive — just by formatting the drive with the new OS (i.e., will it automatically boot as my startup drive if Mojave or Catalina are installed on the SATA)?

Want to make sure I do this correctly so I don't have issues after replacing the HDD.

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I think you'er mixing things which don't really work.

● A Fusion Drive is when a small PCIe/NVMe SSD is setup as a cache drive to a slower SATA drive. Trying to create a dual SSD Fusion Drive won't be effective, the I/O throughput will be somewhere halfway between the two I/O throughputs.

● The speed of the PCIe/NVMe drive is much faster than the SATA III (6.0 Gb/s) HDD or SSD your system also supports. Setting up a dual independent drive config is by far the best setup internally. Here we get at least a 512 GB blade SSD and then either use the HDD or if you need fast data throughput (large images or vids) then using a SATA SSD.

● We also have one more drive interface: The external Thunderbolt 2 port which is even faster than either internal interfaces! As an example I have a 2013 MacPro (Trash Can) which has a 2 TB PCIe blade SSD and a set of external TB2 drives my active data drive is a RAIDed SSD and my second is a RAIDed HDD. I have only my OS, Apps & apps scratch space on the internal blade SSD and my current project is on the external SSD. The majority of my internal SSD is left empty so the OS and apps can leverage it for virtual RAM & caching.

And yes you will need to break the Fusion Drive set.

You may want to review RAID architectures as that's the way I would go if you really need the performance! Otherwise just use a dual drive config with a larger blade SSD and your current HDD or if really needed a SATA SSD.

No one has found dual SSD Fusion Drives workable! Some have tried setting up a JBOD set but that doesn't really work either Non-RAID drive architectures as the I/O speed difference between the two internal I/O interfaces is not the same causing sporadic I/O.

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Forget the idea of fusing multiple SSDs together. As @Dan mentioned, it is not worth it.

Regarding your other questions:

You do not need to split the fusion drive via terminal beforehand.

Nor do you need to format the SSD you are installing, beforehand.

– Physically install the new SSD in place of the 1TB spinning disk

– Upon boot, hold option + R to boot into internet recovery, or, boot to a Mac USB installer

– While in recovery mode, Open Disk Utility and format the new SSD you installed. Also format the internal Apple "blade" SSD.

– Then, when you boot via your USB installer, begin the Catalina install process, and select the newly installed SSD as your destination

– You will wind up with 2 drives. (1) Your newly installed SSD, where the Mac OS is installed. (2) The old blade SSD, empty, which you can use for whatever.

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Further thoughts:

– It isn't worth the time, effort, performance "gain", or added complexity (albeit, it isn't much to begin with) to "partition" the SSD into multiple drives. (Ie. Installing the Mac OS on one partition, and user/data and apps on the second partition – or whatever flavor of slicing and dicing you're thinking of)

– Use the leftover blade SSD for fast scratch space (video editing programs, audio, etc.)

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Thank you both the speedy replies. I've read a ton on subject, but really needed a bit more clarification before I cracked my machine open. Nice to have multiple options for reconfiguring.

To clarify, I'm swapping my HDD for SDD because the HDD is failing and I really needed to get more life out of this machine before I drop another couple grand on a newer machine (I typically buy refurbs). I'm hoping I'm able to do that with the replacement drive. While I have it open, would you recommend checking any other components for wear/issues before I close it back up?

For future reference when the time comes, would you both recommend getting an iMac with the largest single SSD I can afford (vs another fusion)? I assume single SSD machines are PCIe and not SATA?

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I've seen problems when the drives haven't be broken apart if you try reusing them. If you take both out then you won't need to worry. Both the SSD and the HDD have pointers in their master block areas which is why you need to alter the setting.

Review this guide: The Ultimate Guide to Apple’s Proprietary SSDs. If you can get a 512 GB or larger blade SSD and then keep the blade as your boot drive. Forget Fusion Drives! At the time they came out the cost of SSD's was still quite high and was a way to gain the speed but not the cost. Today SSD's are cheaper! Sadly, the custom Apple SSD's are still high even the 3rd party SSD's from OWC and Transcend. Don't get suckered into getting an M.2 if you really want something to last.

Yes! Get a SSD only iMac for your next system. But, don't go crazy going with the biggest!

Dual drive configs are still better! The issue is the amount of read/writes a drive goes through. SSD's have a limit unlike HDD's. While HDD's do have a weakness being mechanical most deep storage is still off of HDD's!

Don't get me wrong here I love SSD's too! It gets down to which tool is best for the condition and the risks if you get into trouble. If you are a heavy creator you want the dual drive setup. If you're just a dabbler then a single SSD drive is all you'll need.

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To break the Fusion drive should be quite simple, I believe: Boot the iMac from an Arch Linux installation USB stick, do lsblk to identify the two drives, then do dd if=/dev/urandom of= /dev/<disk> for both disks to erase all information at the beginning of the disks (just write a few MBs), and that should do the job. This procedure of course will erase all data on both drives, so be sure to back up before.

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No need to jump to another OS, besides Arch Linux does not support APFS file system it only can work with HFS+

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Again, you DO NOT need to do this. It is totally optional.

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