The partition size is extended, but the file system remains the original size when you extend an NTFS volume

C:\>DISKPART

Microsoft DiskPart version 5.1.3564

Copyright (C) 1999-2003 Microsoft Corporation.
On computer: MYSERVER

DISKPART> list volume

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 0     D                      Removable     27 PB
  Volume 1     E   DATA_VOL    NTFS   Partition   2000 MB  Healthy
  Volume 2     C   Windows     NTFS   Partition   4001 MB  Healthy    System 

The Diskpart utility's extend filesystem command extends the file system on the volume.

DISKPART> select volume 1 

DISKPART> extend filesystem

DiskPart successfully extended the file system on the volume.

DISKPART> exit

Leaving DiskPart...

Read More ->>