Brand new install of an internal SSD on my 2017 iMac.

den.thed, thanks for your answer! Since I had decided to replace the drive internally, I posted the question that way. The fact is the SSD drive is still sitting next to me, so it is good I waited. Your solution seems the best for my level of expertise.

BTW, the SSD drive was purchased from OWC along with the iMac kit to make the change feasible.

Given my level of expertise though, I would run the steps to be taken, like:

1. Connect new SSD to iMac with Universal Drive Adapter.
2. Using CCC to clone HD. Q: does CCC format the SSD? Or do I have to do it manually?
3. Hit Start

Now, because of my original and misleading question, I assume the second paragraph refers to the SSD being already installed, correct? If that is so, then would you be kind enough to help with Steps to follow after #3 above.

Please, and thank you very much!!

den.thed, again, thanks!

I got it done, opened iMac and installed the new SSD drive! The only minor glitches I found were 1) the screen connectors were not at all as shown in the OWC video, but I chose logic rather than panic and was able to solve that. 2) it took longer to get the glue strips off the body & screen than it was shown on the video, but again, patience and "wrist-grease" won the day.

Now, to the next issue:

When starting the iMac for the first time, I got the Lightning and USB connector symbols plus an apple support website address on a black screen but had no way of selecting either. Tried all the Option+R command and a couple of other iterations with no results.

So, I decided to plug in the old drive, using the Universal Drive Adapter, and presto! It started.

Now, it is seeing both drives, the SSD on top of the Macintosh HD on the Disk Utility window, but refuses to see the new SSD as the startup drive.

I restarted the Mac with the Option+R mode and showed me the Disk Utility window, I unmounted the Hybrid HD and closed all and restarted, but the Mac HD keeps showing up.

Funny thing is the computer appears to be working from the newly installed drive, to judge by the blazing speed I now see in the system; which makes me all the more want to get it all "right" and do away with the old - and flawed - HD.

Any thoughts?

Please and thank you...

den.thed, hello! Just wanted to provide an update; I got the problem solved !! I had help of course, yours and the Support team at OWC. The solution was to do a fresh instal of the Mac OS into the new SSD drive, followed by an incremental backup from the old Mac HD to the new SSD using Carbon Copy Cloner. Then erasing and unmounting the volumes of the Mac HD, doing a restart, and voila!!

Old is out, new is in, and working like "buttah"....

Again thanks to you and all who offered help and suggestions!

Have a great week!!

den.thed, thanks for your reply. Will proceed and get back here if any issues.

Thanks again!!