1. Managing data is independent from the physical storage
2. Migration to new graphical environments is faster
3. It is possible to make changes on the presentation level without affecting the other two (business or data access layer)
4. As each tier is independent it is possible to use different sets of developers
5. Since the client doesn’t have direct access to the database business logic is more secure
6. When one tier fails there is no data loss, because you are always secure by accessing the other tier.
Scalability: Each tier can scale horizontally. For example, you can load-balance the Presentation tier among three servers to satisfy more Web requests without adding servers to the Application and Data tiers.
Performance: Because the Presentation tier can cache requests, network utilization is minimized, and the load is reduced on the Application and Data tiers. If needed, you can load-balance any tier.
Availability: If the Application tier server is down and caching is sufficient, the Presentation tier can process Web requests using the cache.
References:
one[
^] &
two[
^]
-KR