2013 MacPro, 64gig, iOS 10.10.3, 3.5 GHz 6-Core Intel Xeon E5, LR file is on its own 1TB SSD drive as well as Cache separate from the program. LR irata file is 60 gig and the number of images is approximately 180,000. I just added approximately 5,700 images which was 167 gigs. Using LR6, it ate up all of my memory with its grab of the file cache. Did the same thing with LR5. LR5 only took a max of 13 gig. With LR 6, the memory went negative.
Not Impressed. I think I will stay with LR 5 for a while.