http://aurthurxlc.github.io/Aurthur-2017/Centos-7-extend-lvm-volume.html
注意：
逻辑卷（LV）扩容
逻辑卷扩容是指把空闲的VG扩展到现有的LV上，创建好VG后只需要操作：
[root@localhost ~]# vgdisplay
--- Volume group ---
VG Name centos
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 6
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 2
Act PV 2
VG Size 238.99 GiB
PE Size 4.00 MiB
Total PE 61182
Alloc PE / Size 9982 / 38.99 GiB
Free PE / Size 51200 / 200.00 GiB
VG UUID DaVeeu-7kph-xczl-SnGx-EgfH-PRAa-vGlTwc
[root@localhost ~]# lvextend -l +100%FREE /dev/centos/root
这样就可以把所有Free PE扩展到root LV下
