In a four site indexer cluster, the configuration that stores two searchable copies at the origin site, one searchable copy at site2, and a total of four searchable copies is site_search_factor = origin:2, site2:1, total:4.
This configuration tells the cluster to maintain two copies of searchable data at the site where the data originates, one copy of searchable data at site2, and a total of four copies of searchable data across all sites.
The site_search_factor determines how many copies of searchable data are maintained by the cluster for each site. The site_replication_factor determines how many copies of raw data are maintained by the cluster for each site. For more information, see Configure multisite indexer clusters with server.conf in the Splunk documentation.