Based on BayouBills recent upgrades and the conflicting opinions he has received recently I pose this question based on SONAR usage
 
1 Who has one single drive for everything OS/program/audio/vst libraries
 
2. who has two drives?  one for OS/programs and separate for audio and projects?
 
3 Who has more than two drives and separate audio and projects to one and large vst libraries and the like to another?
 
Any comments on performance gains by separating the data you found OR issues you had are appreciated.

2

5 here:
OS, Audio, Sample Libs, Storage, Dual boot and Storage
No bad issues.
Perks: lots 'a' space and easy backup via .bat files.
It's been so long since I didn't so it this way that I couldn't tell you if there's a down side to not doing it.

3)
 
I have:
an OS drive with programs
a data drive with sonar projects, downloads, and other data
a sample drive for all my instrument sounds
a backup drive

I know there have been just a few responses so far, but appears that no one is having issues by spreading out data, CONTRARY to the experts upstairs .....

I haven't even ventured upstairs to see. 
 
for years the experts have said that this is the way to go.  separate drives for OS, data and samples.  who is saying that is not the way to go now?

Beagle
3)
 
I have:
an OS drive with programs
a data drive with sonar projects, downloads, and other data
a sample drive for all my instrument sounds
a backup drive

I also have 3 internal drives in the same format as Beagle. I backup all my data on a 3TB External drive. Never had any issues with this system. My OS/Programs SSD drive is however running out of room (I have about 70GB left in the 250GB).
I'd love to get a 2 or 3 TB SSD drive for my samples.......when prices drop.....

are you talking about the one expert who said put everything on one drive in bill's thread upstairs.
 
I don't consider him an expert.  it's all perspective.

There was a post in the Computer Forum about having one large SSD (2-3 TB drive) instead of having 3 seperate drives. With all the available powerful components for the newer PC's, this might be a valid argument...........but if the drive fails, all your work/PC can be at risk. Even having an external backup to this, you'll have to install EVERYTHING on the new drive (instead of replacing a single smaller drive....i.e. the 3 drive system).  

Mesh
There was a post in the Computer Forum about having one large SSD (2-3 TB drive) instead of having 3 seperate drives. With all the available powerful components for the newer PC's, this might be a valid argument...........but if the drive fails, all your work/PC can be at risk. Even having an external backup to this, you'll have to install EVERYTHING on the new drive (instead of replacing a single smaller drive....i.e. the 3 drive system).  

yes, one large SSD might be a valid replacement for 3 separate disk drives.
 
I think, tho, if I went that route, I might go with at least 2 SSD drives instead.  just for safety's sake.