Need advise on Fusion drive (iMac: 27" retina, mid 2017)

[True.Panda]

Hi, guys!

Yesterday I finally made an upgrade of my Fusion drive and replaced it with Samsung 850 SSD and Samsung 970 EVO blade.
As soon as I assembled my iMac back, it started loading from Mojave that I previously installed on Samsung 850 SSD, when it was connected as an external drive. That gave me opportunity to format Samsung 970 EVO after boot and measure both HDD speeds. All worked fine w/o sleeping issues and w/o OWC temperature sensor. Sintech long version adapter was used.

Now. Everything works just fine, except the fact that I can't read the 1 Gb Seagate drive when I plug it externally. This drive was used on pair with a 32 Gb Apple blade to form a Fusion drive.

Upon investigating the issue, I've found that the Fusion technology stores info on both drives, and separately the information can't be read.
Since I have a lot of important files on old Fusion drive, I decided to put it back again with Apple blade and backup everything I need from them. Plugged both back, iMac boots, no issues so far.

My question is, what should be the best approach to move files, I need from Fusion to new HDDs I'm planning to install inside my iMac and how I can make that big Seagate will work separately w/o Apple 32Gb blade, when I plug it later as external drive?

Some information on iMac: 27" retina, mid 2017
Thank you in advanced for your answers.

I also want to thank a guy who suggested not to put stripes after assembling the iMac back, but just put screen back and hold it in place with a paper tape, to ensure that everything works correctly for several days and iMac can be sealed safely.

 

[glenthompson]

Multiple options. Best bet is to clone fusion drive to another external drive. Then use the clone to restore to the new drives. You can also split the fusion before removing and then be able to access the data.

Instead of having to put the fusion drive devices back in the iMac couldn’t you restore from your backup? You do have a backup don’t you? If not, do that first before touching any more hardware.

 

[True.Panda]

Multiple options. Best bet is to clone fusion drive to another external drive. Then use the clone to restore to the new drives. You can also split the fusion before removing and then be able to access the data.

Instead of having to put the fusion drive devices back in the iMac couldn’t you restore from your backup? You do have a backup don’t you? If not, do that first before touching any more hardware.

Thank you very much, human!

I actually have a backup, but only for documents - the standard iCloud option.

The important files I'm talking about, is a huge pictures archive, which doesn't fit space there. I don't want to loose them, since it represents my photography hobby for the last 3 years.

I think I'll copy everything to the SSD, which later be used as a boot drive and then split Fusion to use 1 Tb Seagate as external drive.

I didn't know about Fusion split option. It looks like the best option for me.

 

[Fishrrman]

I agree with glenn about the cloning.

You can download CarbonCopyCloner for free, and it will work in free mode for 30 days.

Use CCC to create a clone of your (old) fusion drive onto an external drive.
That clone will now "look and feel" exactly as did the fusion drive, yet it's "all on one drive" and no longer has anything to do with "fusion".

With this done, you can put your NEW drives back into the iMac.

MY SUGGESTION:
DO NOT "fuse" the new drives together.
Instead, let each drive "be its own drive".
Put the OS, apps, and basic accounts on the fastest drive -- the blade drive.
Keep "large libraries" on the slower SATA SSD. (or, leave it as it is)

You'll know where everything is, and I've never had problems managing 2, 3, 4 drives on my desktop at once (although this seems to befuddle more than a few users...)

 

[True.Panda]

Carbon Copy Cloner worked like a charm!
Now I'm using SSD plugged as an external drive, which contains exactly the same Mojave I was running on Fusion drive.
Looks like everything in place and I'm ready to make next move - place both: SDD and new Blade inside iMac and get rid of the old Seagate and Apple blade.
Once it is done, I'll run Carbon Copy Cloner again, this time to move everything from Evo 850 to Evo 970 blade, since it's x6 times faster.