what type of cheap (like not $50K) hard disk arrays are there that can handle millions of small text files (1 to 50 Kb, most <5 Kb)?

SCSI 15K drives might not be good enough, what is the next step in faster I/O than SCSI? can a good cacheing controller with large memory help when dealing with huge numbers of files?

the total storage size doesn't need to be huge, 18 GB might be ok, although around the 50 Gb range would be better.

thanks