Best hard drive configuration for PS and Mac Pro?

[lukasdp]

My 2.8 Quad core is in the mail. As I up grade the RAM over the next few months I'm curious as to your thoughts on the best possible hard drive configuration to get the best performance out of photoshop.
In terms of scratch disks and boot drives, should PS be installed on the boot drive or not? separate from the scratch disk? how big should the scratch disk be? my files in PS never get bigger then 1gig, and I only have 1 or 2 open at a time. solid state drives sound fancy but I dont much care if PS takes 10 seconds or 1 second to load, I want it to run fast no open fast so I dont think I need to get into SS drives but I'm open to your thoughts!
my macPro will come with a 1TB 7200 HD and I have a 1TB 7200 external connected Via Firewire 800, is this an option for the scratch disk or should that be internal?

thanks.
~Lukas.
www.lukaspeters.com

[creativeretouch]

I would set up your scratch disk on your boot drive as long as you will leave enough room there. The best performance from your hard drives you will get if you wlll leave them empty

The good rule is to leave about 20% of your hard drive empty.

About your scratch files - you can check their size if you would go to the info palette and click on the right upper option button - choose "Palette options" and choose from menu your desired informations.

[lukasdp]

ok thanks, OS and scratch on the same drive.
Iv'e read elsewhere that PS should be installed on a different drive then the scratch disk.
Is there any major performance difference to doing this?

[creativeretouch]

I think scratch disk on OS drive must be much faster. You mentioned your boot disk is 1 TB? So do not worry.
I do not see any point to use an external disk here.

Different case is if you work with movies. Files are so big with HD (2K, 4K, 6K) video that you need a boot disk with software and an external disk where you keep your files.

Do you use CS5 and are you on 64-bit processor and a lot of RAM? It will use RAM and than scratch disk anyway.