10

Front end Tier/ 

Mid Tier/ 

Back end Tier/ 

End Users 

Web Server  Application Server 

Database Server 

(B2C) 

D a t a   G e n e r a l 

Web Server 

Application 

Database 

Server 

Server 

Storage 

Server 

Laptop 

D a t a   G e n e r a l 

C o m  m   

P  o 

r  t 

S D 

B a y   

N  e t  w o r  k s 

B  a y S t  a c  k  4 5 0    1 2 T    

S  w i  t 

c h 

U p l i  n 

k    M o d u l e 

1 3 

1 4 

1 5  1 6 

1 

2 

3 

4 

5 

6 

7 

8 

9 

1 0 

1 1 

1 2 

1 

2  3 

4 

5  6 

7  8 

9  1 0  1 1 1 2  1 0 0 

1 0 

F   

D  x 

A c t 

i  v i t 

y 

Webswitch 

Computer 

Partners 

(B2B) 

D a t a   G e n e r a l 

Fig. 2.2. A Multi Tier Data Center Architecture

2.2

Cluster based Data Centers

A cluster based data center is a special type of a cluster based Web server. Fig 

ure 2.2 depicts the typical architecture of a cluster based data center or network server

consisting of three layers: front end Web server, mid level application server, and back 

end database server. A Web server layer in a data center is a Web system architecture

that consists of multiple server nodes interconnected through a System Area Network

(SAN). The front end Web server provides static or simple dynamic services. The Web

resources provided by the first tier are usually open to public, and thus, do not require

authentication or data encryption. Hence, the latency of the client's request in this layer

is usually shorter than in the application servers.

The mid tier, called the application server, is located between the web server and

the backend database. The application server has a separate load balancer and a security