Basic tuning hints (ctd)

Use decent quality network cards
3com 3c509, Intel Etherexpress Pro/100
Cuts down on the amount of interrupts/sec during busy periods

Always put in more RAM than you need
If you hit swap, squid will die

Look into using multiple aufs (linux/solaris) or diskd (BSD) cache_dirs instead of a single UFS cache_dir

Profile your cache to find a suitable number of disk IO threads/queue slots
Use these limits - and max_open_disk_fds in squid.conf - to prevent squid from spiralling down during load spikes