Genghis
I recently did the upgrade myself to a Samsung 850 EVO, 1TB drive. It came with the software to clone my old hard drive, and it was a pretty easy, painless process.  After I did it I realized I was really only using about 300GB on the boot drive, so I partitioned it using a utility called EaseUS to a little over 400GB for  boot drive and the rest for samples.  I copied my Superior Drummer 3 libraries over to that partition so that it loads faster.

Thanks for this referral. I snooped around and found an 850 EVO SSD that I'm thinking of getting. It's a 250 GB mSata. And, yep, Samsung page talks about the cloning software that does all the work under the hood. I've read a clean install is the best, but I'm not sure I want to get into all that. Anyway, thanks for sharing your experience with the Samsung SSD. 

Thanks everyone for weighing in! I've got a better understanding now....
 
So, I'm looking at a 250GB SSD, which isn't mammoth, but should work if I have the right file management. Sample libraries can get huge. Can I keep them on the slower HDD and still get the speed advantage in Sonar if my OS (Windows 10/64) and Sonar are on the SSD? 
 
What I'm not clear on is what files should go where, given the option of a limited-size SSD and a companion, larger, HDD. For example, samples (which can be large libraries) "load" into Sonar and VSTi's, right? They aren't streaming, where throughput is crucial, right? I can live with the samples loading slower, if that's the trade-off of having them on the slower HDD, instead of hogging space on the faster, size-limited SDD.
 
I'm trying to get the fastest, most robust, performing CPU I can get for Sonar. 
 
Thanks!
 
 

Some sample libraries are streamed off the disk rather than being loaded into RAM, unless you've a huge amount of RAM. Even then the instrument's software may be coded to stream samples from disk anyway.

As for partitioning, it can have beneficial effects on an HDD under some circumstances. The "classic" one being to partition an HDD into at least two partitions, with the first one created being used for audio spooling. This makes a difference because the first partition will be using the outer section of the disk platters and, since the outer edge of a spinning disk has the highest angular rotation speed, data on it passes through the disk heads faster than that towards the centre of the disk. The speed reduction as data is read/written nearer the physical centre of the disk difference is quite significant

Which means you get the fastest sequential read/write speed out of the "outside" partition of an HDD. The downside is marginally slower seek times but when streaming big audio files the faster read/write pays off.

All of which is irrelevant to SSDs. The only benefit of partitioning them is to make organising your data easier.

Genghis
I recently did the upgrade myself to a Samsung 850 EVO, 1TB drive. It came with the software to clone my old hard drive, and it was a pretty easy, painless process.  After I did it I realized I was really only using about 300GB on the boot drive, so I partitioned it using a utility called EaseUS to a little over 400GB for  boot drive and the rest for samples.  I copied my Superior Drummer 3 libraries over to that partition so that it loads faster.

 
In your case, two smaller SSDs would have been better than one single large one.

Kev999

Genghis
I recently did the upgrade myself to a Samsung 850 EVO, 1TB drive. It came with the software to clone my old hard drive, and it was a pretty easy, painless process.  After I did it I realized I was really only using about 300GB on the boot drive, so I partitioned it using a utility called EaseUS to a little over 400GB for  boot drive and the rest for samples.  I copied my Superior Drummer 3 libraries over to that partition so that it loads faster.

 
In your case, two smaller SSDs would have been better than one single large one.

Haven't pulled the trigger on any SSD yet. In fact, I'm already eyeing the 500GB, instead of 250. The more Sonar-related files (audio, sample data, etc.) I can keep on the SSD the better the results of having an SSD running Sonar, is that correct? 
 
 

If you have been having issues and your system say has been used  on line a lot, you've installed a bunch of apps you no longer use, and on and on, the system gets messy and next thing you know you have 150 processes running in the background. 
A clean install is not technically complicated to do, it's real simple, Sit there installing the stuff you use. 
In my case it's all in a portable drive or on disks. But I still go to web sites to make sure I have the latest versions and compare the version numbers first. 
It just takes longer but most of that time is just waiting for the installs, so like me I'm doing other stuff during the task otherwise it's pretty boring. 
You end up with everything all up to date and running smoothly. And I believe there's a big performance and stability boost. 
Cloning saves time but to me is a short cut and can just bring along the same ghosts that haunted your old system. 
If you old system is in tip top shape and your not sure how to re install everything then cloning might be better for you. 
 

The idea of Junctions as I described above enable you to move folders wherever you like. This way you can start using your SSD and getting the performance boost without having to reinstall anything.
 
Run the command window as administrator.
 
c:\>mklink /J "C:\ProgramData\Cakewalk\Command Center\Downloads" "E:\ProgramData\Cakewalk\Command Center\Downloads"
 
 Junction created for C:\ProgramData\Cakewalk\Command Center\Downloads <<===>> E:\ProgramData\Cakewalk\Command Center\Downloads

I have a 250 SSD. I keep my OS, Sonar projects and small sample library's on it.
The rest go on a 1 TB or a 500 GB HDD.
I like the projects on the SSD with Sonar because they open lightening fast and Audio is written to disk rather fast as well.
 

To add my 2 cents:
I'd put the OS, programs, FXs and Samples on the SSD and have an external HDD linked via your SATA connector as the recording drive. The reason for this is that an SSD has a limited number of writes over its lifetime. Accessing samples doesn't require any writing (unless you bounce/freeze the track) so you SSD will last longer if you are only reading files. 
I record live instruments and the huge file sizes and multiple takes would exhaust the SSD more quickly. HDDs don't suffer from this as you can write/erase/write to them an infinite number of times without effect. The connection speed via SATA is more than fast enough to accomodate read/write speeds for the audio tracks, while the SSD will boost the performance of the programs and VSTs.
Hope this makes sense.

Your SSD most likely came with a CD or a link to download a data migration tool. 
 
Each of my Samsung SSD's came with a link to download the Samsung Data Migration software which I used to migrate all of my data from the Old SSD's to the higher SSD's.   It has worked well without any glitches.