Kill Permanent Sleep Proccess

I’m running Redhat 6.2 and sometimes it hangs. Is the a why of killing this? the proccess looks like this:

000 D root 1788 1 0 60 0 – 348 down_f Mar07 ? 00:00:00 [tar]
000 D root 2144 2142 0 60 0 – 310 down_f 05:15 ? 00:00:00 tar -cvf /dev/nst0