> my 'cache_dir' option in squid.conf is:
> cache_dir aufs /reiser/squid-cache-2 10240 32 512
> My system spec is:
> RedHat 9 (2.4.20-20.9)

Ok, before you keep torturing yourself that aufs is not working in =
your case,
I advice to let this squid setup run for some time, and let it be used.
Then use cachemgr to have a look at the 'Async IO Function Counters'.
Guess if these are none zero, then your aufs setup will be fine.