Mike, being a little intrigued by this I decided to use the Nef file as in my last post and build it up to a reasonably large size using copy layers and stamping as WIP layers, going from the original file size as reported in PS 103.4MB up to 1.52GB.
Saved file size in Windows = 1.57GB. Saving the file took approx 25-30 seconds. Therefore once again even though your file a little larger this seems to be taking much too long @ 2.5 minutes
I agree and I wonder if it has to do with the WD Caviar Green. Maybe it goes to sleep to save engergy but even still that is a long time to write that data.