为何不能进行：parted对磁盘分区进行重置大小呢？

为何不能进行：对磁盘分区进行重置大小呢？

Number  Start   End     Size    File system  Name     Flags
 1      1049kB  10.0GB  9999MB               primary
 2      10.0GB  20.0GB  9999MB               primary
 3      20.0GB  30.0GB  10.0GB               primary

[root@iZ2vchlrqdxr6zzdu7x59qZ ~]# parted -s /dev/vdb resizepart 3 20GB
Warning: Shrinking a partition can cause data loss, are you sure you want to continue?
[root@iZ2vchlrqdxr6zzdu7x59qZ ~]#

我这边执行了命令后，打印还是：10GB大小

Number  Start   End     Size    File system  Name     Flags
 1      1049kB  10.0GB  9999MB               primary
 2      10.0GB  20.0GB  9999MB               primary
 3      20.0GB  30.0GB  10.0GB               primary

请问下是什么原因不变化呢？