1)
Проверяем размер диска (/dev/sda)
[root@localhost
~]# lsblk
NAME
           MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda
              8:0    0   20G  0 disk 
├─sda1
           8:1    0    1G  0 part /boot
└─sda2
           8:2    0   19G  0 part 
├─centos-root
253:0    0   17G  0 lvm  /
└─centos-swap
253:1    0    2G  0 lvm  [SWAP]