LVM (Logical Volume Manager) is a subsystem that allows using different areas of one or several hard drives as a single logical volume. The size of logical volume file systems is not limited to a single disk, as a volume can be located on different disks and partitions.

LVM basic designations:

  • physical volumes (PV, Physical Volume) — disk partitions or entire disks;
  • volume groups (VG, Volume Group) — physical volumes grouped into a single disk;
  • logical volumes (LV, Logical Volume) — partitions created on physical space of the volumes group.

An LVM storage supports one format of virtual disk format — RAW. Learn more in the official documentation.

Peculiarities of LVM in VMmanager

  • VMmanager does not configure LVM on the cluster node. The volume group name must be specified manually before adding a node into the cluster.
  • After the storage is added, the VG name is displayed on the Disk space tab of the cluster node card.
  • Only VM disks are stored in LVM each of them in a separate LV with the name "<vm_id>_<vm_name>". VM and OS images are stored outside the LVM.

When adding a cluster node with LVM, VMmanager calculates the number of VG on the node and searches for the VG with the specified name: 

  • if it finds one or several VG with the appropriate name, the node will be added;
  • if no VGs are found, the error message will be shown and the node won't be added.

Example of LVM storage connection

  1. Connect to the cluster node via SSH.
  2. Initialize physical volumes (PVs) to operate with LVM:

    pvcreate /dev/sda6 /dev/sda7 /dev/sda8

    /dev/sda6, /dev/sda7, /dev/sda8  — PV block devices

  3. Create the volume group (VG): 

    vgcreate vg_vmmanager /dev/sda6 /dev/sda7 /dev/sda8

    vg_vmmanager — VG name

    /dev/sda6, /dev/sda7, /dev/sda8  — PV block devices

  4. Specify the VG name when creating a cluster or connecting storage to a created cluster. For more information, see Creating a cluster, Managing cluster storages.