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Using Replication for Scale-Out

You can use replication as a scale-out solution; that is, where you want to split up the load of database

queries across multiple database servers, within some reasonable limitations. Because replication works from the distribution of one master to one or morę slaves, using replication

for scale-out works best in an environment where you have a high number of reads and Iow number of

writes/updates. Most Web sites fit into this category, where users are browsing the Web site, reading

articles, posts, or viewing products. Updates only occur during session management, or when making a

purchase or adding a comment/message to a forum.

Replication in this situation enables you to distribute the reads over the replication slaves, while still

enabling your web sen/ers to communicate with the replication master when a write is reąuired. You

can see a sample replication layout for this scenario in Figurę 16.1, "Using Replication to lmprove Performance During Scale-Out”.