Migrating Fusion Drive to SSD/SSD-Flash Combo

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Migrating Fusion Drive to SSD/SSD-Flash Combo

Hi. I’m upgrading my 2017 iMac 5k Retina 4.2Ghz by swapping out the old 3TB Fusion Drive (getting increasingly sluggish), and installing a 4TB SSD (Crucial MX500) + 1TB SSD Flash-Blade (OWC Aura Pro x2) combination.

Physical install not an issue.

My nervousness concerns the migration of the Fusion Drive’s OS + Data over to the new SSD combo.

So, considering the following possible setup’s that I may proceed with, how would I migrate OS+data given the circumstances?

I may want to either:

Save and boot OS off 1TB Flash-Blade and use 4TB SSD for data,

or,

save all data, OS and boot from 4TB SSD, just using the 1TB flash-blade as parallel project drive to copy over current project (large post production ProTools/AdobePremiere projects) to work on, utilising the fastest drive access available for hi disk/cpu session,

or,

re-Fuse both drives (if possible? apparently doable from terminal?) and let OS allocate and manage storage distribution.

I’d like to think I’m tech-savvy but when it comes to drive migration and the possibility of borking my system and losing all data within I’m clearly not confident enough and can be rightfully be considered a novice at best.

Any help appreciated and thanks in advance 🤘🏻

iMac 27″ 5K, macOS 12.6

Posted on Dec 8, 2022 3:10 PM

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Answer 1

MartinR

Level 7

24,258 points

Dec 10, 2022 9:10 AM in response to Jimmy_Game

What version of macOS are you running? Up to & including Catalina (10.15.x) you can use Carbon Copy Cloner to clone your current system from the Fusion drive to either of the new SSDs ... but you will need an external enclosure for the SSD you want to clone to. (Cloning the system drive is more challenging if you are on Big Sur or later.)

Also, consider that it may be better in the long run just to do a fresh install from scratch on the new SSD.

If it were me, I'd use the Blade as the boot drive; it will be on the internal PCIe bus which is significantly faster than the SATA bus the MX500 will be on.

IMHO there is no sense to trying to fuse the two SSDs and may not even be possible. It's not what the Fusion design was intended for and it could increase the risk of data loss over the long term if the fused drives ever separate (remember, it's only software that holds them together).

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Answer 2

MartinR

Level 7

24,258 points

Dec 13, 2022 10:35 AM in response to Jimmy_Game

Jimmy_Game wrote:

"I’m so sorry but to ask for more but you really need to talk to me as though I know nothing. What you say to help is very kind but I’m realising my incompetence as it’s only raising more questions ..."

Based on your questions and comments in your latest post, and their implications, here's my best advice - engage a competent, local Apple authorized service provider to do this work for you.

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Answer 3

MartinR

Level 7

24,258 points

Dec 12, 2022 7:02 AM in response to Jimmy_Game

The only way the old OS would be on the MX500 would be if you cloned the Fusion drive to the MX500. Don't do that. Just copy your data files - you can use the Finder to do that or even CCC if you prefer. Just don't clone the Fusion drive to the MX500.

Note also that in this scenario, Migration Assistant will not be useful, so you won't be able to migrate user accounts; you will have to create your user accounts new on the blade after you install macOS on it (and, of course, also install your apps).

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Answer 4

Old Toad

Level 10

215,502 points

Dec 9, 2022 2:34 PM in response to Jimmy_Game

I would do the following: boot OS off 1TB Flash-Blade and use 4TB SSD for data. I believe the Flash-Blade drive would be faster and 1TB is plenty of space for a boot drive.

How much data is on the current fusion drive, or how much free space do yo have left?

But wait! There more! (Sounds like a TV ad?)

You may have some 3rd party software installed that is causing the slowness. You could determine if this is the cause before going to the effort to swap out all that hardware and then end up with lower than expected performance.

So with that in mind download and run Etrecheck. Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to paste the report in your reply.

Then we can evaluate the report to see if we can determine the cause of the problem.

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Answer 5

Jimmy_Game Author

Level 1

4 points

Dec 9, 2022 3:47 PM in response to Old Toad

Hi. Thanks for reply.

I have 500GB’ish left of 3TB (this is also part of the reason for upgrade, to get enough memory installed and get a couple more years out of the old fella).

The upgrade is pretty much essential I think as fan’s on constantly and the HDD has been abused for 5 years now and could fail at any moment.

I’ll do your diagnostics and get back with a report shortly.

In the meantime, do you have any advice on how exactly to perform the migration for your suggested best practice (OS on blade, Data on SSD)?

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Answer 6

Jimmy_Game Author

Level 1

4 points

Dec 10, 2022 2:25 PM in response to MartinR

Hi. Thanks for the info, very helpful.

I’m on Monterey, what’s the status with Carbon Copy Cloner with that, what’s the complications?

I have a 2.5” usb 3.1 gen2 external enclosure ready when needed.

Ok, so you’re second to mention the blade-4-boot/SSD-4-data combo option so I’ll go with that and scrap the ssd fuse option.

(Also just a side note, I have an external 4tb HDD which I’ve used Time Machine to back up on to just incase).

so, my confusion is this:

The original Fusion Drive is a virtual drive spread across two physical drives, HDD for data, SSD pcie for OS and selected data for quick access based on usage. If I do I a fresh OS install on the new blade and boot from there, does it have access to everything on the new SSD without issues and function as normal?

or,

Having freshly installed the new OS on the new blade, if I clone/copy/restore the old Fusion Drive onto the new MX500 SSD is the old installed OS carried over along with my data, thus giving me two OS’s to boot from, the fresh OS installed on new blade, and the old OS copied over onto the new SSD? If so, this is undesirable and is there a way to just extract only non-OS data from old Fusion Drive and install it onto new SSD achieving the preferred result of fresh OS on new blade, and only data on new SSD?

sorry if I’m asking silly or unnecessary questions but I don’t want to ‘f’ this up.

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Answer 7

MartinR

Level 7

24,258 points

Dec 11, 2022 12:14 PM in response to Jimmy_Game

Jimmy_Game wrote

The original Fusion Drive is a virtual drive spread across two physical drives, HDD for data, SSD pcie for OS and selected data for quick access based on usage.

That's not how the Fusion drive works. The SSD & HDD that make up the Fusion drive are coupled as a single logical unit; the SSD portion is essentially buffer RAM to optimize (aka speed up) apparent drive performance. macOS is not specifically stored on the SSD portion of the Fusion drive.

If I do I a fresh OS install on the new blade and boot from there, does it have access to everything on the new SSD without issues and function as normal?

If you mean that both the blade & the MX500 are both installed in the iMac, the answer is yes. Ditto if the MX500 is in an external enclosure.

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Answer 8

MartinR

Level 7

24,258 points

Dec 11, 2022 12:21 PM in response to Jimmy_Game

Regarding your last question about cloning/copying/restoring the old Fusion Drive onto the MX500, I would not do that.

What is your intended procedure to install the blade, the MX500 and remove the Fusion drive?

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Answer 9

Jimmy_Game Author

Level 1

4 points

Dec 11, 2022 12:55 PM in response to MartinR

Hi Martin.

Ok thanks.

The final outcome will be to have 1TB blade installed on internal PCIe bus replacing the Apple original blade, (32Gb maybe?), and a 4Tb SSD installed via Sata cable connection replacing the Apple original 3Tb HDD.

So, 3TB HDD/SSD Fusion Drive replaced by 4Tb-Sata/1Tb-SSD-PCIe combo.

Going by advice received and working requirements I would like the 1Tb-SSD-Blade to carry the OS and boot from. I would use the 4Tb-Sata-SSD to use as storage.

The working practice would then be to drag any large project I’m currently working from the 4Tb-Sata-SSD onto the 1Tb-SSD-Blade where I can optimise speed and minimise latency whilst working, returning the project session folder back onto the 4TB-Sata-SSD once finished.

My issue is migrating the current Fusion Drive data and OS over to new SSD drives.

I need a fresh OS install onto new 1Tb-blade, and all data, minus the old OS, moved from the Fusion Drive onto new 4Tb SSD.

Where/how do I start?

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Answer 10

Jimmy_Game Author

Level 1

4 points

Dec 12, 2022 12:58 AM in response to MartinR

Perfect Martin, thanks.

One last thing.

Following either of you options, would the old OS still be present on the MX500 as it was on the Fusion Drive I backed up from. If so, is it removable, will cause issues, or does it go unnoticed and is inconsequential?

I’m not worried about old OS file size, it’s just the booting/operating complications that may be present with having two OS’s on one system.

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Answer 11

Jimmy_Game Author

Level 1

4 points

Dec 13, 2022 9:21 AM in response to MartinR

Hello Martin. Thanks again.

I’m so sorry but to ask for more but you really need to talk to me as though I know nothing. What you say to help is very kind but I’m realising my incompetence as it’s only raising more questions.

So is copying the data files as simple as dragging the Macintosh HD drive folders (Applications, Library, System, Users) over onto the MX500. Am I right?

What is CCC?

If I fresh install a OS on the blade do I need to install every single app I have? And does my user account no longer exist?

What other things should I expect to encounter if I go ahead with upgrade and want my system to operate normally?

Can you write me a step by step instructions of the OS/Data transfer operation. I have all the hardware, drives/enclosures etc. I just need clear instructions that guide me to transfer OS on Blade and Data on MX500.

Assume I know nothing!

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Answer 12

Jimmy_Game Author

Level 1

4 points

Dec 13, 2022 11:46 AM in response to MartinR

ok will do.

but before I do I’d like to run my own step by step process by you (having deduced what I could from previous messages). What do you think, yay or nay?

Blade in external enclosure. Hook up and download OS
MX500 in external enclosure. Hook up and copy Macintosh HD drive folders over (Applications don’t copy over though)
Backup/Time-machine Fusion Drive on to additional external drive
Remove Fusion Drive HDD+Blade from iMac and install new Blade and MX500
Boot up from blade
Create user account
reinstall apps

Sound ok, or get a pro?

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Answer 13

MartinR

Level 7

24,258 points

Dec 11, 2022 5:21 PM in response to Jimmy_Game

Jimmy_Game wrote

The working practice would then be to drag any large project I’m currently working from the 4Tb-Sata-SSD onto the 1Tb-SSD-Blade where I can optimise speed and minimise latency whilst working, returning the project session folder back onto the 4TB-Sata-SSD once finished.

I think that's an irrelevant & inconvenient workflow. Since both drives are SSDs there will not be any meaningful difference in operating speeds that you would notice in real life unless you are doing some super-duper-special-heavy math crunching or maybe very heavy production video rendering or the like ... are you planning to mine Bitcoin?

My issue is migrating the current Fusion Drive data and OS over to new SSD drives.

I would back up the data from the Fusion Drive to the MX500 in an external enclosure.
Make a second data backup on yet another external drive. (You can never have too many backups.)
Then put the blade in an external enclosure and install macOS on it.
Then remove the Fusion drive (blade & HDD) from your iMac and replace them with the new blade & MX500.

-or-

Back up the data from the Fusion Drive to your MX500 in an external enclosure.
Make a second data backup on another external drive.
Then remove the Fusion drive (blade & HDD) from your iMac and replace them with the new blade & MX500
Then use either a bootable installer drive or Internet Recovery to install macOS on the newly-installed blade.

Just be sure to back up your data before doing anything else!

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Migrating Fusion Drive to SSD/SSD-Flash Combo

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