Using a Mechanical drive with the APFS file system may not be ideal - How to upgrade your iMac

[UtterDisbelief]

Is there a way to turn off Spotlight Indexing ? ... I don't know of any way to disable it on just the platter drive if you have both an SSD and platter drive in your build.

All you need to do in that case is drag the platter drive icon from your desktop (or Finder) into System Preferences / Spotlight / Privacy.

 

[trs96]

Here's is a video of Luke Miani testing the speed of a 5400 RPM MBP laptop drive that has Catalina installed. Shockingly slow. The read/write speeds are about average for a USB 2.0 flash drive ! One minute and 45 seconds to boot to the desktop. This is more like using a desktop PC from 1995.

 

[trs96]

All you need to do in that case is drag the platter drive icon from your desktop (or Finder) into System Preferences / Spotlight / Privacy.

That can give you the option to omit everything from Spotlight searches but doesn't disable Spotlight from doing the indexing. The terminal command is necessary to disable the indexing from happening on a platter drive.

"Exclude this location from Spotlight searches."