I Just came across a very good article by Clara Ko summarizing the concept behind Space-Based Architecture on Java Pulse. The article is based on our recent white paper Scaling Spring Application In 4 Steps. Clara's article is available here. I highly recommend reading it.
I particularly liked the way Clara summarized the problem with tier-based architectures:
GigaSpaces argues that tier-based architecture is the nemesis to linear scalability. In fact, the architecture itself is the bottleneck, not unoptimized component. This is because in a tier-based architecture, as scability patches are introduced, the communication between the tiers become more complicated and expensive. The complex interaction between tiers and between physical machines in the deployment cause problems with latency and data consistency. Possible problems with tier-based architecture are bottlenecked access to the database, bottlenecked access to a centralized messaging provider, messaging overhead, network latency, inefficient clustering, and unreliable failover recovery. GigaSpaces addresses each of those problems by providing a platform that enables space-based architecture.
Couldn't say it any better.
