I have had several hard drives plugged into my computer for sometime now. Just this week however, it is running at a near standstill. Blue spinning circle for several minutes at a time. Just trying to upload photos can take half an hour. I have closed down and optimized my catalog at least 3 times. What is the problem. I can't spend 2-3 hours just trying to my photos into the catalog.
If you are using Lightroom 6, then please turn off the Graphics Processor from Lightroom preferences.
Go to Lightroom Preferences from the Edit menu
Click on Performance tab
Uncheck the Graphics Processor
Let us know if that helps.
What version of Lightroom? What operating system?
Are you doing a lot of brushing or spot healing on each photo?