Also known as replication groups , a buddy pool is an optional construct where each instance in a cluster may be configured with a buddy pool name. Think of this as an 'exclusive club membership' where when selecting buddies, BuddyLocator s that support buddy pools would try and select buddies sharing the same buddy pool name. This allows system administrators a degree of flexibility and control over how buddies are selected. For example, a sysadmin may put two instances on two separate physical servers that may be on two separate physical racks in the same buddy pool. So rather than picking an instance on a different host on the same rack, BuddyLocator s would rather pick the instance in the same buddy pool, on a separate rack which may add a degree of redundancy.