Replacing Fusion Drive with SSD Question

[topgazza]

Reading lots of slightly different issues an solutions on this depending on the users situation. So slightly concerned
I have a 2013 iMac 21.5” with a fusion drive. They appear to be two separate drives, SSD and HDD. So far so good. I’ve removed the HDD and installed the new 1tb SATA SSD. Before I switch on are there any issues I should be aware of
Will my iMac boot up to the 128gb SSD blade and see the SSD as a to be formatted drive ?
Or could/should I just go with the new SATA SSD as the sole drive ?
I will be restoring with Time Machine so I assume my data etc will go onto the new SSD

any help appreciated

 

[Fishrrman]

IF you have already replaced the platter-based drive with an SSD
and
IF the iMac is closed up,
then
My recommedation is...

DO NOT "re-fuse" the internal drives.
(by the way, the old internal SSD portion of the fusion drive will be unreadable with the HDD portion removed, but you probably already know this).

Instead, you will need to boot from either a backup or from internet recovery.

Internet recovery is:
Command-OPTION-R
at boot

If you're connected via wifi, you'll need your wifi password.

ALTERNATE COURSE OF ACTION:
I understand that more recent versions of time machine backup drives may be "directly bootable" to some subset of the OS utilities so that you can do your "restore" directly from the backup drive.
I don't use tm and have never used it, but if this works, you don't need internet recovery.

In any case, when you get to the Mac OS utilities, you'll need to initialize/erase the new SSD first.
If you're using OS High Sierra or earlier, erase to Mac OS extended with journaling enabled, GUID partition format.
If you'll be using Mojave, erase to APFS, GUID partition format.

Then do the tm restore to the NEW SSD.

The original 128gb SSD will also need to be erased.
I would consider installing a "fresh copy" of the OS onto it.
REASON: It can then become an "emergency boot drive" if you ever have problems booting from the new SSD.
You always want to have a "second, independently-bootable drive" somewhere close-at-hand...!

 

[topgazza]

Brilliant. Thank you and very clear
Only problem I have are broken LCD data cable pins. I sneezed when refitting the screen and it pulled the connector out of it socket on the motherboard. I have fitted a replacement OEM cable but no Apple logo. I have another on it’s way just in case but otherwise I have to spend on a new iMac

I could go for the new Mac Mini but I have to buy a monitor as well with speakers and web cam. I like the iMac. Thinking about a refurb but finding a 21.5 with 1tb ssd is quite hard. Some of the later ones are almost as expensive as new.

 

[volkwagen1300]

Fishrr:

Can you please clarify - the old SSD portion is no longer readable once its HDD fusion mate is removed? If so, how would one erase and install fresh copy of the OS on the original SSD as you mentioned at the end of your reply? Or do I not understand something?

I ask because I can see picking up a 27" fusion iMac at some point and swapping in a new SSD, and am trying to figure out the details.

 

[dcmaccam]

Can you not just remove the fusion drive and at the same time replace the ssd part with a 1Tb pcie ssd. I realise that that involves stripping down a lot more of the machine. You could also install a sata ssd in place of the fusion drive.

 

[Fishrrman]

Well, if the iMac is broken, my advice is...
Get a new Mini, a display, and "start over".

It's probably not worth paying to get the iMac repaired at 8 years old.
You'll have to open it up again (if necessary) and take the new SSD back out.
Get an external enclosure and use it as a backup drive for the new Mini...

 

[raoulco]

I should probably create a new post because my story is quite long and I don't want to gatecrash someone else's post but it is the same subject; but before I do, let me ask this: iMac 27" Retina 2019 - Model ID19,1 with Fusion Drive: if I want to remove & replace the Fusion drive with a SSD NVMe, can I retain the HDD portion of that Fusion drive, erase it and use it as a normal internal storage drive? Or should I remove it completely from my machine? Why I ask is because I've already done that, and my machine is very unhappy: kernel panics, shutting down & restarting for no reason, blinking folder with question mark etc. Could the culprit be the 'old' HDD that's still in my machine? It shows on my desktop as a separate Hard Drive.