Just for fun I timed loading up Sonar with approximately 40 GB of samples, all from an SSD drive and presumably into memory only (?),   and copying approximately the same amount of data from an SSD drive to a regular SATA drive.  
 
It took sonar just under 7 minutes to load; completing the copy took just under 6 minutes.   
 
Now clearly writing to a regular drive is going to be way slower than reading from an SSD drive ... so ... what's taking all that time with sonar?    I've got a suspicion:   Sonar, or kontakt, or Windows, is writing all that loaded data to a working file located somewhere on my system disk (regular SATA).
 
I don't believe it's going to the paging file, it is set at a rather low size on the SSD manufacturer's recommendation (basically that the system should not use a paging file):  800 MB on a system with 64 Gb of memory.   (edit) -- confirmed this last, by changing to a very large paging file entirely on an SSDD drive --- no significant change in load time. 

nm .. bad lead

williamcopper
It took sonar just under 7 minutes to load; completing the copy took just under 6 minutes.

Loading requires parsing the data - e.g., assigning to keyboard ranges and MIDI channels, separating attacks if you're streaming from disk, etc. A straight copy is just a bit-for-bit file transfer, no intelligence required.

Here's another idea:   some sorting routine used by the software is using, by default, a temporary disk file.   That could well be Kontakt but it might be Sonar too.   Nothing in memory could take that long, no matter how much parsing is required. 

From storagereview.com:
 
An SSD does not have a mechanical arm to read and write data, it instead relies on an embedded processor (or “brain”) called a controller to perform a bunch of operations related to reading and writing data. The controller is a very important factor in determining the speed of the SSD. Decisions it makes related to how to store, retrieve, cache and clean up data can determine the overall speed of the drive. We won’t get into the nitty-gritty details for the various tasks it performs such as error correction, read and write caching, encryption, and garbage collection to name a few. Yet, suffice to say, good controller technology is often what separates an excellent SSD from a good one.