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[pve-docs.git] / pve-storage-lvm.adoc

LVM Backend
-----------

Storage pool type: `lvm`

LVM is a thin 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.


.Storage features for backend `lvm`
[width="100%",cols="m,m,3*d",options="header"]
|==============================================================================
|Content types  |Image formats  |Shared   |Snapshots |Clones
|images rootdir |raw            |possible |no        |no
|==============================================================================

Examples
~~~~~~~~

List available volume groups:

 # pvesm lvmscan