Multiple drives question

[bufster23]

I am purchasing a computer that has 3 SATA drives. I also have a SSD drive. I know this has been discussed a million times but I can't find the info. I want to dedicate the drives for performance 1) my operating system on one drive 2)Photoshop on the other 3)Saved files/projects on another 4)Scratch disk.
Which drive should be the SSD.. since it is the fastest?
Also, the system has 12 GB of ram and my projects never exceed 4 or 5GB on the Scratch status bar. Am I correct in thinking I won't need a scratch disk at all, and so I can make a raid configuration with 2 of the satas drives?

 

[dv8_fx]

I'd use the SSD for OS. It's always a good idea to have a scratch disk.

.... but that's just me.

 

[smoke]

SSD for OS and all installed programs/games as it is faster for MoBo to cache data to RAM, CPU, GPU and back.
IF any of other drives are the same make and model you can create mirror ride as it will use 2 HDDs as one. Both of theme will have same info in case if one dyes your photos projects and other unique information is safe.