Raw vs. cooked file systems for cache?

I've been doing some reading on caching proxies, and most people state that
you'll get better performance if you don't rely on the OS for your file
system management and instead use raw filesystem space for storing the
cache. Has anyone played with this for squid that is not reselling it (i.e.
don't consider their code to be proprietary or trade secret)?

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Jon Williams                                              Speed of
lightning,
Public Network Access                                     Roar of thunder,
Deere & Company                                           Fighting those who
309.765.5748                                              Rob and plunder.
williamsjon@jdcorp.deere.com                                --Underdog
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