Lots of good information at Tweakers Page
What I would do is...
All programs on SSD, with project and temp files on hard drive 1 Harddisk usage/space problem with Premiere Pro ... |Adobe Community
All source files on hard drive 2
Experiment to see if output is faster going to hard drive 1 or 2
What I do is in reply #6 for my hardware list in https://forums.adobe.com/message/6536849
My suggestion is get another good SSD and use your current one (if it is a decent one) for the OS/Application files plus let Adobe put the Media Cache/Media Cache Database files in the default C: drive location. Put your project, media and the rest of any project files on the second SSD. When you essentially finish a project, move the files on the second SSD to the hard disk drives for archiving and backup. To keep your C: drive clean then you can delete all Media Cache/Media Cache Database files and if you have to reopen any project they will quickly regenerate.
I take this to the extreme I use one of my Samsung T1 (now a new T3 model is available) USB 3.0 SSD's as my second SSD and this way I can walk from my laptop to my desktop with the current project and/or plug in different second USB 3.0 SSD and instantly change projects.
So you're recommending to use something like the 950 Pro M.2 as the main HD with apps and media cache and then use an additional SSD (850 Pro) for project files, etc.? Currently I'm using the 850 Pro as my main drive and was going to purchase the 950 Pro as my media cache/project/etc drive. Would you suggest I use it as the main drive instead? 512 GB for both drives. I'd like to get the 960 Pro, but don't see it being released for quite some time.
No just the opposite, Use a SATA III SSD like the 850 Pro for the OS/Applicatioins and used the 950 Pro M.2 for your project files. That is how my i7-5960X system is running. The SM961 M.2 1 TB is going to start being available in very limited quantities in early August. I hope to have one when that happens. Your main drive does not need the high speeds of the M.2 SSD once you boot up and have Premiere running it is mostly memory resident so your project/media files get the best performance using the M.2
Thank you for the confirmation. I figured that would be the best way but wanted to make sure. Would you suggest I wait for the SM961?
If you need the 1 TB work space and you do not mind waiting it might turn out to really be slightly less expensive than some of the forecasts and definitely less than two 512GB 950 Pro's