Home > Storage > Unity XT > Virtualization, Cloud & Applications > Dell EMC Unity: VMware vSphere Best Practices > Asynchronous replication
Dell Technologies recommends including a flash tier in a hybrid pool where asynchronous replication will be active. This is applicable to both the source and the destination pools.
Asynchronous replication takes snapshots on the replicated storage objects to create the point-in-time copy, determining the changed data to transfer and maintaining consistency during the transfer. Consider the overhead of snapshots when planning performance and capacity requirements for a storage pool that will have replication objects.
Setting smaller recovery point objective (RPO) values on replication sessions will not make them transfer data more quickly, but smaller RPOs will result in more snapshot operations. Choosing larger RPOs, or manually synchronizing during non-production hours, may provide more predictable levels of performance. Additional information can be found in the Dell Technologies Unity: Replication Technologies white paper.