It has occurred to me that I have seen no defragging tool which makes use of temporary storage on a second drive spindle when it is available. CPU loading is light, but head seek activity, I'm sure, dominates the performance issues. Moreover, I am curious about the amount of data which is moved per operation.
To give you my context, I am working with numerous virtual machine image files, the smallest of which is about 4GB, and the largest is around 60GB. Defragging a drive loaded with this sort of content takes a long time, and I would be delighted to see that time reduced.