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