/etc/multipath.conf

devices {
    device {

        all_devs                yes
        no_path_retry           fail
    }
        device {
                vendor                  "SYNOLOGY"
                product                 ".*"
                path_grouping_policy    multibus
                failback                immediate
                path_selector           "round-robin 0"
                rr_min_io               100
        }
}