6.3.8.2Example of load balancing for improved performance

Suppose that the enterprise has the following characteristics:

Uses a Directory Server that includes 1.5 million entries in support of one million users

Each user performs ten directory lookups per day

Uses a messaging server that handles 25 million mail messages per day

The messaging server performs five directory lookups for every mail message that it handles

This equates to ten million directory lookups per day for users, and 125 million directory lookups per day for email; a total of 135 million directory lookups per day.

With an eight-hour business day and users spread across four time zones, for example, the business day (or peak usage) across four time zones extends to 12 hours. Therefore, the service must support 135 million directory lookups in a 12-hour day. This equates to 3,125 lookups per second (135,000,000 / (60*60*12)).

Table 6-2 Calculating Directory Server load

Access type

Type count

Accesses per day

Total accesses

User Lookup

1 million

10

10 million

 

 

 

 

Email Lookup

25 million

5

125 million

 

 

 

 

Combined accesses

 

 

135 million

 

 

 

 

Total

 

135 million (3,125/second)

 

 

 

 

 

88 Designing the replication process