Linux – How to Extend Volume Group to Physical Volume Size

I started off with a 25GB hard drive, and wanted to extend it to 150GB. I used fdisk to extend the /dev/sda2 partition from 26GB to 149GB. lsblk shows the following information:

NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda             8:0    0  150G  0 disk
├─sda1          8:1    0    1G  0 part /boot
└─sda2          8:2    0  149G  0 part
  ├─rhel-root 253:0    0   76G  0 lvm  /
  └─rhel-swap 253:1    0    3G  0 lvm  [SWAP]
sdb             8:16   0   50G  0 disk
└─rhel-root   253:0    0   76G  0 lvm  /
sr0            11:0    1 1024M  0 rom

fdisk -l shows the following output:

Disk /dev/sdb: 53.7 GB, 53687091200 bytes, 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/sda: 161.1 GB, 161061273600 bytes, 314572800 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b0bb3

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200   314572799   156236800   83  Linux

Disk /dev/mapper/rhel-root: 81.6 GB, 81595990016 bytes, 159367168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/rhel-swap: 3221 MB, 3221225472 bytes, 6291456 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

I put in a second 50GB disk and was able to use vgextend and xfs_growfs to add it to the volume group. Now, the rhel volume group is 76GB. However, I don't understand why the volume group isn't 200GB, since sda2 is 149GB. The results of pvscan are below:

  PV /dev/sda2   VG rhel            lvm2 [<29.00 GiB / 0    free]
  PV /dev/sdb    VG rhel            lvm2 [<50.00 GiB / 0    free]
  Total: 2 [78.99 GiB] / in use: 2 [78.99 GiB] / in no VG: 0 [0   ]

It shows /dev/sda2 as <29.00GB, which is surprising to me. I would have expected it to be 149G as shown in lsblk. I tried doing vgextend rhel /dev/sda2, and it says that the physical volume /dev/sda2 is already in the volume group rhel, which makes sense. I'm just struggling to understand why df -h only shows 76GB when I would think it would be 200GB. Here is the output of df -h:

Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   76G   11G   66G  14% /
devtmpfs               3.9G     0  3.9G   0% /dev
tmpfs                  3.9G     0  3.9G   0% /dev/shm
tmpfs                  3.9G  9.0M  3.9G   1% /run
tmpfs                  3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sda1             1014M  217M  798M  22% /boot
tmpfs                  783M     0  783M   0% /run/user/1000
tmpfs                  783M     0  783M   0% /run/user/0

Please let me know what steps I can take to make /dev/mapper/rhel-root the full 200GB it should be.