As per this bug report on the squid-cache.org website: http://www.squid-cache.org/bugs/show_bug.cgi?id=1371 we should not be building squid with --enable-truncate It seems that the chance of a problem with this is slight, but we should be guided by the developers opinions on what is a sensible configure option.
This issue was opened for the new, featured version (3.0), but in Fedora we have the old one, stable version (2.5). Please reopen it if doesn't work for the stable one.
I asked about this - refer the bug report above again - the comment about using truncate is relevant for squid-2.5 and squid-3.0. (Apparently the disk I/O, even if refactored, is pratically identical between Squid 2.5 and Squid 3.0.)
Okay.