In estimating read traffic, consider the following:
How many searches per second are expected?
What types of searches are expected?
For example, unique ID searches, wildcard searches, exact match searches.
What is the estimated peak search rate?
What is the estimated average search rate?
How many unindexed searches are expected?
An unindexed search means that the database is searched directly, instead of the index file. Unindexed searches occur either when the All IDs Threshold is reached within the index file used for the search, when no index file exists or when the index file is not configured in the way required by the search.
Unindexed searches are generally more time consuming than indexed searches.
Are searches concentrated in a particular data center or geographic region?
If one data receives proportionally more search traffic than other data centers, it might be worth placing additional, replicated servers in this data center to balance the load.
Are searches concentrated at a particular time of day?
How many searches are anticipated from within the firewall?
How many searches are anticipated from outside the firewall?
If read performance is crucial to your enterprise, see Chapter 10, Designing a Scaled Deployment for suggestions on deploying a directory service that is scaled for reads.