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Model A1419 / EMC 3070 / Mid 2017 / 3.4, 3.5 or 3.8 GHz Core i5 or 4.2 GHz Core i7 Kaby Lake Processor (ID iMac18,3) / Retina 5K display. Refer to the older iMac Intel 27" Retina 5K Display (Late 2014 & 2015) guides as the system is very similar.

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To Fusion or Not - after transplanting my MacBook Air 512GB SSD


After much toying around I finally transplanted successfully my old MacBook Air 2015 512GB SSD into my 27” iMac 2017. While at it I also decided to drop in a Crucial MX500 1TB.

Will a Fusion setup be faster than my old Mac 512GB SSD solo?

I take it a Fusion setup will probably not be as stable. But I backup regularly.

I’m very happy with the speed of the iMac post-transplant.

Thank you for any advice.

- Carl

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You don’t gain any benefit with a Fusion Drive setup with two SSD’s. In fact you loose performance! The best setup is a dual drive setup.

  • Use the blade SSD as your boot drive as well as hosting your Apps and nothing else!
  • Use your SATA drive as your data drive.

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Thank you Dan.

What would be the best way to proceed in terms of executing your suggestion?

Thanks again.



Required steps:

● Backup your data!

How to split up a Fusion Drive

● Setup the blade SSD as your boot & app drive - Format & install OS - APFS

◆ Leave the rest of the drive empty! Ideally 1/4 for a 512 GB/1 TB

● Setup the SATA drive as your data drive - Format - HFS+ if HDD, APFS if SSD


Hi Dan.

Big thanks.

I've done all that. Wish I could show you a screen shot.

I should have asked. How do I create Symbolic Links from "Macintosh HD" (which is the Apple blade to "Macintosh HD2" which is the storage drive.

I have something like 150GB in my Documents folder and another 100GB in Pictures which all really should be living on the HD2.

I thought a symbolic link would be the best way to do it?

I searched for creating symbolic links but strangely they weren't that helpful. I did get a good setup going using the following only to find problems with Downloading in Safari and Airdrop. So I gave up and thought I'd ask you. I suspect it's better to not remove the folder with the 'rm' command.

*All my data is still living on the portable external drives.

Admins-iMac:~ Carl$ pwd


Admins-iMac:~ Carl$ sudo rm -rf ./Downloads/


Admins-iMac:~ Carl$ ln -s /Volumes/HD2/Downloads Downloads

Admins-iMac:~ Carl$ ls -al


Simple put what are you trying to do? Give me an example or two.

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Carl will be eternally grateful.
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