Install parted
root@matrix:/home/sunkan# aptitude install parted
Run partprobe on the blockdevice
root@matrix:/home/sunkan# blockdev --getsize64 /dev/xvde 21474836480 root@matrix:/home/sunkan# partprobe /dev/xvde root@matrix:/home/sunkan# blockdev --getsize64 /dev/xvde 42949672960