Web 2.0 ushered in a wave of new communication services that require different infrastructure and architecture than the services that preceded them.  In this presentation from the O'Reilly Velocity Conference, John Fowler of Sun Microsystems describes several new developments by Sun to help meet the needs of modern Web applications.

One of the big changes in hardware is the move from faster clock speeds to multi-core and threading models.  Another hardware change is the availability of very high memory machines, up to 1 terabyte.  This improves throughput and performance.  The last big change is the integration of SSD flash memory into the hardware stack, providing a layer faster than disks but cheaper than RAM.  This combination gives significantly improved I/O performance and throughput for a similar cost to high RPM HDD drives.  This allows modern consumer web apps to scale horizontally with infrastructure that matches application usage.