pve-storage-lvm.adoc

LVM Backend

Storage pool type: lvm

LVM is a light software layer on top of hard disks and partitions. It can be used to split available disk space into smaller logical volumes. LVM is widely used on Linux and makes managing hard drives easier.

Another use case is to put LVM on top of a big iSCSI LUN. That way you can easily manage space on that iSCSI LUN, which would not be possible otherwise, because the iSCSI specification does not define a management interface for space allocation.

Configuration

The LVM backend supports the common storage properties content, nodes, disable, and the following LVM specific properties:

vgname

LVM volume group name. This must point to an existing volume group.

base

Base volume. This volume is automatically activated before accessing the storage. This is mostly useful when the LVM volume group resides on a remote iSCSI server.

saferemove

Zero-out data when removing LVs. When removing a volume, this makes sure that all data gets erased.

saferemove_throughput

Wipe throughput (cstream -t parameter value).

Configuration Example (/etc/pve/storage.cfg)

lvm: myspace
	vgname myspace
	content rootdir,images

File naming conventions

The backend use basically the same naming conventions as the ZFS pool backend.

vm-<VMID>-<NAME>      // normal VM images

Storage Features

LVM is a typical block storage, but this backend does not support snapshot and clones. Unfortunately, normal LVM snapshots are quite inefficient, because they interfere all writes on the whole volume group during snapshot time.

One big advantage is that you can use it on top of a shared storage, for example an iSCSI LUN. The backend itself implement proper cluster wide locking.

Tip	The newer LVM-thin backend allows snapshot and clones, but does not support shared storage.

Table 1. Storage features for backend lvm

Content types	Image formats	Shared	Snapshots	Clones
images rootdir	raw	possible	no	no

Examples

List available volume groups:

# pvesm lvmscan