Replace Fusion Drive in 27" iMac

The Fusion Drive in my 27" iMac is becoming very slow. It is running macOS Ventura 13.7.1 and I wish to replace this with a faster SSD. Any suggestions?

iMac 27″ 5K, macOS 13.7

Posted on Jan 23, 2025 10:16 PM

Reply
Question marked as ⚠️ Top-ranking reply

Posted on Jan 24, 2025 1:14 AM

Opening an Apple Computer, especially an iMac, will require special tools to get it open


It will also require some very special knowledge, by the user, to properly disconnect various cables within the computer


All this, before one gets to removing and replacing the SSD drive of this Fusion Drive


An alternative to extend the life of this machine


From another User Tip on running the computer entirely from an External SSD Drive


No opening of computer required


Use an external SSD as your startup disk … - Apple Community


24 replies
Sort By: 

Feb 5, 2025 4:26 PM in response to Servant of Cats

Hi Servant of Cats.


You mentioned above: with an external SSD I'd still be using all of the parts of my Mac except the Fusion Drive. (It would now be just a "second drive", and if you had no reason to believe it was actually failing, you could use it an extra backup, or for extra storage.)


To use the old Fusion Drive as a second drive for storage, how would I get it to appear in the Sidebar and Desktop, so I could drag and drop Folders into it?


Reply

Feb 28, 2025 12:04 AM in response to Servant of Cats

Hi Servant of Cats,


Apologies for having taken so long to respond to you. I've been thinking too much about my situation. I still need advice, and more knowledge, before proceeding with the external SSD.


Will the new external SSD (connected to the 27" iMac via a USB-A cable with an adapter) be replacing the existing Apple SSD Controller of 28GB capacity? This is indicated as an APPLE SSD SM00321.


I am planning to purchase an SSD (LaCie) to be my new startup drive. Which would be better, a 1TB or a 2TB SSD? Is larger better, or is smaller OK? I need some education as to what it actually does.


Many thanks for all your previous comments and suggestions,

peterpatter.

Reply

Feb 28, 2025 7:27 PM in response to Servant of Cats

Hi Servant of Cats,


Thanks so much for your advice. I like your second suggestion above. However, my 2017 iMac only has USB-A ports and an ethernet port on the back. Can I get an adaptor so one of these ports can become a USB-C / Thunderbolt port, to get the USB 3.1 Gen 2 speed? I've decided to go for the LaCie 2TB SSD. My Time Machine backups are on a 4TB external SSD.


Again, many thanks,

peterpatter.

Reply

Mar 1, 2025 10:57 PM in response to Servant of Cats

Hi Servant of Cats,


Thanks so much for your information. As I've never, so far, had need for the USB3 ports, I had forgotten that they were there. How stupid can I be? To transfer files between my iMac and my MB Air (M1 chip), is a cable between the respective USB3 ports the best way of doing this?


At the moment both Macs are running OS Ventura. Is it necessary for them both to be on them same OS when transferring files via a cable, or wifi, or does this not matter?


By the way, based on information from you, and others, I will soon be purchasing a 2TB LaCie SSD to be my new startup drive.


Many thanks,

peterpatter.

Reply

Mar 2, 2025 8:57 PM in response to peterpatter

Hi Servant of Cats,


It's me again. At my local Apple Store, the LaCie rugged 2TB SSD is indicated as being suitable for an iMac (Retina 5K, 27-inch, 2019–2020). As my iMac is a 2017 model, is it OK to go ahead with the purchase? The 2TB model costs quite a bit more than the 1TB SSD.


Many thanks,

peterpatter.


Reply

Mar 20, 2025 11:03 PM in response to Servant of Cats

Hi Servant of Cats,


Thanks so much for that useful information. Does it matter if the 27" iMac is on macOS Ventura 13.7.4 with an Intel Core i5 processor, while the 13" MBA is running with Ventura and an Apple M1 chip? If I upgraded the MBA to macOS Sequoia, would they still be compatible with each other for transferring files between them, using either a thunderbolt cable or iCloud?


Do you know how far I can upgrade my iMac OS, or is Ventura the limit for it? I've read somewhere that I probably can't go up beyond Ventura.


By the way, I've now bought a 2TB OWC Envoy SSD to use as the startup drive for my iMac, so I'll be using the information that you and others have provided, to proceed with this. Wish me well with speeding up my iMac.


Cheers,

Peterpatter.

Reply

Mar 31, 2025 12:29 AM in response to Servant of Cats

Hi Servant of Cats,


Thanks for your valuable information. It seems my 2017 iMac can only go as far as Ventura, but my M1 MB Air can go to Sequoia. Should I upgrade it? Will there be any problems with transferring files, etc. between them?


I now have my 2TB OWC Envoy SSD, so will be setting it up on my 2017 iMac with Ventura, as the startup drive and transferring all my data to it. I trust that all will go go smoothly thanks to your valuable guidance. While I am at it, should I consider increasing my Memory from 8 GB to 16 GB?


Many thanks for all your assistance,

Peterpatter.





Reply

Mar 31, 2025 6:00 AM in response to peterpatter

peterpatter wrote:

Hi Servant of Cats,

Thanks for your valuable information. It seems my 2017 iMac can only go as far as Ventura, but my M1 MB Air can go to Sequoia. Should I upgrade it? Will there be any problems with transferring files, etc. between them?


There shouldn't be much of a problem with transferring individual files. However, whenever you upgrade macOS, there's a possibility that Apple will have decided to change the format of the Music / TV (iTunes) database or the Photos (iPhoto) database.


If that is the case, you can usually take the libraries forward a version or two (e.g., from Ventura to Sequoia), and the applications will automatically upgrade the library format as needed. But once the libraries are converted, it may be more difficult to take the library back.


I don't know that this has happened with Ventura vs. Sequoia, specifically; just that it happens sometimes.


I now have my 2TB OWC Envoy SSD, so will be setting it up on my 2017 iMac with Ventura, as the startup drive and transferring all my data to it. I trust that all will go go smoothly thanks to your valuable guidance. While I am at it, should I consider increasing my Memory from 8 GB to 16 GB?


You can upgrade RAM on your 27" iMac – and if running Activity Monitor while you are doing stuff that uses a lot of RAM shows that 8 GB is not enough, you could consider doing so. (If you were doing heavy Photoshop work – or running virtual machines – on that 27" iMac, you might consider putting in 32 GB.)


I would suggest buying RAM for the 27" iMac only from Other World Computing. Macs can be picky about RAM, and the other "go to" Mac RAM vendor (Crucial) seems to have gotten out of that particular business.


You cannot upgrade RAM on any Apple Silicon Mac. If your M1 MacBook Air has only 8 GB of RAM, there is no way to upgrade that short of replacing that Mac with another one that has more.

Reply

Replace Fusion Drive in 27" iMac

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.