Disks, Filesystems and LVM¶

LVM puts a flexible layer between disks and filesystems, so you can grow storage without downtime.

Warning

pvcreate and mkfs destroy existing data. Check the device with lsblk first.

Add a new disk with LVM¶

lsblk -f
sudo pvcreate /dev/sdb
sudo vgcreate vg_data /dev/sdb
sudo lvcreate -n lv_app -L 20G vg_data
sudo mkfs.xfs /dev/vg_data/lv_app

sudo mkdir -p /srv/app
sudo blkid /dev/vg_data/lv_app                       # note the UUID
echo 'UUID=<uuid>  /srv/app  xfs  defaults,nofail  0 0' | sudo tee -a /etc/fstab
sudo mount -a && df -hT /srv/app

Use the UUID in /etc/fstab, since device names can change. Always run mount -a after editing, or a typo can break the next boot.

Grow a volume¶

sudo vgs                                              # free space in the group
sudo lvextend -r -L +10G /dev/vg_data/lv_app          # -r also grows the filesystem

XFS can grow but cannot shrink. ext4 can do both, with resize2fs.

Health checks¶

df -h                  # space
df -i                  # inodes (a full inode table looks like a full disk)
lsblk
sudo lvs && sudo vgs && sudo pvs

For Kubernetes volumes see Persistent Storage.