This script will use rsync to keep data in sync on a loop, and then notify you via a Slack webhook how long each iteration took, and how much data was copied.

rysync_data_migration.sh

#!/bin/bash
rsync_source="198.51.60.10:/mnt/tank/dataset/"
rsync_dest="/mnt/tank/dataset/"
slack_token="UYHJ5E74J/B03QSDR6598/8pW72Fl5OOUoFlj53sIccOi6"
get_space="df | grep `echo ${rsync_dest::-1}` | awk '{print \$3}'"
export BLOCKSIZE=1024 
while true; do
    before_space=`eval "$get_space"`
    time_passed=`{ time rsync -aAHX $rsync_source $rsync_dest; } 2>&1 | grep real | awk '{print $2}'`
    after_space=`eval "$get_space"`
    data_transfered=`echo $((after_space-before_space))`
    dt_length=`echo "${#data_transfered}"`
    x=0
    while [ $((dt_length)) -ge 4 ]; do
        data_transfered=`echo $((data_transfered/1024))`
        ((x=x+1))
        dt_length=`echo "${#data_transfered}"`
    done
    case $x in
        0)
            suffix="KB";;
        1)
            suffix="MB";;
        2)
            suffix="GB";;
        3)
            suffix="TB";;
        *)
            suffix="???";;
    esac

    curl https://hooks.slack.com/services/$slack_token \
        -X POST \
        -H 'Content-type: application/json' \
        -d "{\"text\":\"Data Migration has copied $data_transfered$suffix in $time_passed\"}"
done