This IBM® RedpaperTM publication describes the concepts, functions, and practical usage of IBM Easy Tier® Heat Map Transfer (HMT). IBM System Storage® DS8000® Easy Tier is designed to automate data placement throughout the storage system disks pool. Easy Tier generates a heat map. It is a workload activity metric for each extent in a logical volume. With Easy Tier HMT, it is possible to transfer the heat map from a mirrored primary site and reapply it periodically at secondary and tertiary sites by using the Easy Tier Heat Map Transfer Utility (HMTU). This capability helps maintain storage performance after a failover to a remote site. With DS8870 Release 7.5, the heat map transfer supports Metro Global Mirror (MGM) replication topology in addition to Metro Mirror/Global Copy/Global Mirror (MM/GC/GM) functions. This paper is for those professionals who want to understand the Easy Tier HMT concept and its underlying design. It also provides guidance and practical illustrations about the operation of the HMTU. For more information about the general concept of Easy Tier, see IBM DS8000 Easy Tier, REDP-4667. For more information about Easy Tier Server and Easy Tier Application, see the following publications: IBM System Storage DS8000 Easy Tier Server, REDP-5013 DS8870 Easy Tier Application, REDP-5014