Lvm

The Logical Volume Manager device mapper lets us create file systems that span multiple physical disks. When you know the hierarchy, the rest of the concepts become clear. At the hardware level, you have physical disks. These physical disks are divided into “physical volumes”. Physical volumes are then added to “volume groups”, and the volume groups contain “logical volumes”. These logical volumes contain partitions that can be formatted with file systems.

When a disk becomes full, we add a new physical disk, create a physical volume, add it to an existing volume group, and then extend a logical volume. We then resize the partitions (growpart <device> / sfdisk / fdisk / cfdisk) and filesystems (resize2fs <partitione>).

See: LVM cheatsheet

Also see: Linux RAID setup