2009/7/9, oooooooooooo ooooooooooooo hhh735@hotmail.com:
After a quick calculation, that could put around 3200 files per directory (I have around 15 million of files), I think that above 1000 files the performance will start to degrade significantly, anyway it would be a mater of doing some benchmarks.
depending on the total size of this cache files, as it was suggested by nate - throw some hardware at it.
perhaps a hardware ram device will provide adequate performance :
http://www.tomshardware.com/reviews/hyperos-dram-hard-drive-block,1186.html