#stopped the tar and you can see the disk space. 
# df 
Filesystem         1K-blocks      Used Available Use% Mounted on
/dev/md0           287972720 261500468  17691312  94% /


# nohup tar -cpjvf  --ignore-command-error /mnt/mntpoint/longfilesname.tar.bz2  /media/drive1
nohup: ignoring input and appending output to ‘nohup.out’
^C

#then after starting it for a second or two and stopping it I get my space back. 


# df 
Filesystem         1K-blocks      Used Available Use% Mounted on
/dev/md0           287972720 260682408  18509372  94% /

#started it again. 

 df 
Filesystem         1K-blocks      Used Available Use% Mounted on
/dev/md0           287972720 263300048  15891732  95% /

#as you can see I have lost 2 gigs+ of space and /tmp is only 300MB. 
du -csh /tmp
336M    /tmp
336M    total

#now I will stop it.
#see this diskspace taken up.
df 
Filesystem         1K-blocks      Used Available Use% Mounted on
/dev/md0           287972720 263448232  15743548  95% /
#and if I start it again let it run for 3 seconds and stop it all the space comes back. 
df 
Filesystem         1K-blocks      Used Available Use% Mounted on
/dev/md0           287972720 260904568  18287212  94% /