Sharepoint Architecture

We have 3 layer architecture

WFE <Front End Web Server> 
2. Application Layer 
3. Data base Layer 


1. WFE 

share point Installed. 
12-hive structure & virtual drives. 
IIS web sites are hosted. 
servers are clustered on & are in synch. 

2. Application Layer

Share Point provides different services. 
This layer provides those services, like my site hosting, user profile & searching etc. 
One server can be dedicated to particular service depend upon the scalability. 

3. Data Base Layer 

Here we have SQL server installed. 
Here content DB is hosted. 
For moss 2007, it is SQL server 2005. For Share Point 2010, it is SQL server 2008. 
Here servers are clustered on & are in synch. 

* Every layer has load balancer for control the traffic.