If the destination is over burden with other IO then yes, but if there is little activity then there could be something else happening in the replication and or the target are using the same NIC or Ethernet port. Best to use separately. You can see the replication transfer rate in Status > Tasks to review. But if there is a dedicated NIC for the replication on both ends and good controllers even on SATA I have seen on both ends from 5MB/s (usually RAID issue) to 50MB/s+.