Search head Pooling: Pooling here refers to sharing resources. It uses shared storage for configuring multiple search heads to share user data and configuration. It allows users to have multiple search heads so they can share user data and configuration.  Multiplying the search heads helps in horizontal scaling during high/peak traffic times when a lot of users are searching for the same data.  Search Head Clustering: A search head cluster is a group of Splunk Enterprise search heads that share configurations, search job scheduling, and search artifacts, which are the results and associated metadata from a completed search job.  Search head cluster can be utilized in the distributed Splunk deployment to handle more users and concurrent searches, and to provide multiple search heads so that search capability is not lost if one or more search members go down