Server performance hacks age the best out of all the performance optimization techniques I can think of. The same socket descriptor multiplexing tricks that were used to make news servers pump gigabytes of alt.binaries.* a day, in that age of "megabit networking", can be used today to push html and a few pngs very comfortably. Why? because network capacity, memory size and processor speed are growing orders of magnitude faster than network service consumers are being created, making the old network performance hacks far more powerful today (solely focusing on human users here, though even software "users" can be tolerated with more intelligent "push" architectures allowing the server to deliver content to its subscribers at its earliest convenient time.)

Also, changes in kernel architectures and the addition of fast and faster system calls only makes it better, but not different.

Unix (mostly BSD) ftp servers were at some point in the not-so-distant history the only places to get software; Simtel.net run on ONE server with no load balancing. Email? anon.benet.fi scaled really well. Not to long ago, single Unix servers were household names and their admins and systems hackers were Gods.