speed up dd_rhelp

watch_dd_rhelper.sh

# cat `which watch_dd_rhelper`
#!/bin/bash
PREVIOUS=/tmp/previous
LAST=/tmp/last
reset=false

while true; do
    [ "$reset" == "false" ] || reset=false
    cat /proc/$(pidof dd_rescue)/io > $PREVIOUS
    sleep 10
    cat /proc/$(pidof dd_rescue)/io > $LAST
    if [ "x$(diff -q $PREVIOUS $LAST)" == "x" ]; then
        kill -SIGINT $(pidof dd_rescue)
        reset=true
        echo -n "dd_rescue hung, restarting..."
    else echo -n "ok..."
    fi
done

no data read in 10 seconds => give up and try a different area.