Processes in D state

Hi, I have various processes in D state:

Code:

ps axl | grep D

F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
4   104  2579  9109  20   0   5024  2116 refrig D    ?          0:00 cleanup -z -t unix -u -c
4   104  2842  9109  20   0   5016  2088 refrig D    ?          0:00 cleanup -z -t unix -u -c
4   104  3006  9109  20   0   5024  2092 refrig D    ?          0:00 cleanup -z -t unix -u -c
0 10022  4547  4865  20   0   4796  1536 refrig D    ?          0:00 /usr/sbin/postdrop -r
0 10006  4557  4865  20   0   4796  1544 refrig D    ?          0:00 /usr/sbin/postdrop -r

How can i delete this processes?
Why this processes go in D state?

Thank's

 

Hi, thanks for the reply Till.
I think my problem is with vzdump (the server is a virtual server of Proxmox and Openvz)

see here:

http://forum.openvz.org/index.php?t=tree&goto=38812&#msg_38812