Earlier versions of the vSphere Replication appliance had 2 vCPUs. The combined appliance for vSphere Replication 5.6 and later has 4 vCPUs.
If a 4-vCPU vSphere Replication appliance runs on an ESXi host system with 4 or less physical CPU cores per NUMA node, replications that are managed by this 4-vCPU appliance are slower than replications managed by a 2-vCPU appliance.
Run the 4-vCPU vSphere Replication appliance on a host system that has more than 4 CPU cores per NUMA node.
Note: The vSphere Replication appliance might be migrated to another host system with less than 4 cores, for example during host maintenance. Therefore, if your environment contains hosts with 4 or less cores, apply the following workaround.
Deploy additional vSphere Replication Servers in your environment to distribute replications among them, and disable the vSphere Replication Server that is embedded in the vSphere Replication appliance.