I am having trouble after replacing my iMac's SuperDrive with a Solid State Drive (SSD).
I kept the original Hard Disk Drive (HDD) in place. I configured the SDD as the main startup disk and I transferred all the libraries in HDD.
The malfunction is that in the process of rebooting the iMac turns off.
Booting into safe mode the Disk Utility shows the new SSD drive is full, although before rebooting it has used only 90GB out of 480GB. I do the same procedure again, clean install of macOS 10.12, and again the same problem. Any ideas please for solution of this malfunction?
I have to say that if I do not reboot the iMac, it runs excellently, and the SSD drive has the same empty capacity 90GB used out of 480GB.
iMac 21" 2009/late. SSD Kingston 480Gb / macOS 10.12, Sierra.