pvs
vgs
lvs

# RHEL 6
lvextend -L 4G /dev/mapper/rootvg-lv.tmp
resize2fs /dev/mapper/rootvg-lv.tmp

# RHEL 7
lvextend -L 4G /dev/mapper/rootvg-lv.tmp
xfs_growfs /dev/mapper/rootvg-lv.tmp

sudo su -
fdisk -c -u /dev/sdb
n  # new partition
p  # physical partition
1  # first partition, set begin & end blocks
t  # set type
8e # set to Linux LVM
p  # print what we have
w  # write changes

pvcreate /dev/sdb1
vgcreate vg_name /dev/sdb1
vgextend rootvg /dev/sdb1
vgdisplay  # see what we have used and free

lvcreate -L 90G -n lv.sqlmon rootvg
mkfs.ext4 -j -m1 /dev/rootvg/lv.sqlmon  # ext4
tune2fs -i0 -c0 /dev/rootvg/lv.sqlmon

mkfs.xfs /dev/rootvg/lv.sqlmon          # xfs

echo "/dev/mapper/rootvg-lv.sqlmon /sqlmon ext4 defaults 1 2" >> /etc/fstab
mount -a