device=/dev/md0
size="`fdisk -l $device 2>/dev/null|grep -m1 bytes |awk '{print $(NF-1)}'`"
while [ 1 ];
do
    # $RANDOM is too small a number for the drive / drive cache
    rand_size="`shuf -i1-$size -n1`"
    dd if=$device  bs=1 count=1 skip="$rand_size" >/dev/null 2>&1
    sleep 5
done