I have a custom search engine script (written msotly in PHP) that runs fine now (under low load), but when I get about 600 queries per second my load goes to 50!

I need to know speed in terms queries per second that Oracle and MySQL can handle (if they in fact would be my limitation)

Also I am considering Solaris as an OS (vs my Red Hat with reiserFS)

I need several front end servers to act as cache servers with a cental DB (I can't replicate it as it's about 10TB and hope to grow it to about 60TB.

Does anyone have any implementation suggestions?

Which DB format to use? Operating system? Hardware suggestions?

For my central server, can I still get good speed with SATA vs scsi if I put some scsi disks in my front end servers?

I'm VERY open to ideas, thanks!