Block Changes Rate on a Datastore LUN that's under replication

Hi,

As we are observing LUN-to-LUN replication slowness, taking long time to do incremental sync, need to find blocks change rate (per day or per hour etc.,) on a specific LUN (Datastore) mapped to the ESXi hosts.

Please let me know, if there is a way to find the required details through vCenter/PowerCLI/ESXi shell etc.,

Thanks!