add vIOMMU documentation

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

[[storage_lvm]]
LVM Backend
-----------
ifdef::wiki[]
:pve-toplevel:
:title: Storage: LVM
endif::wiki[]

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`::

Called "Wipe Removed Volumes" in the web UI. Zero-out data when removing LVs.
When removing a volume, this makes sure that all data gets erased and cannot be
accessed by other LVs created later (which happen to be assigned the same
physical extents). This is a costly operation, but may be required as a security
measure in certain environments.

`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
snapshots and clones. Unfortunately, normal LVM snapshots are quite
inefficient, because they interfere with all writes on the entire 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 implements proper cluster-wide
locking.

TIP: The newer LVM-thin backend allows snapshots 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

ifdef::wiki[]

See Also
~~~~~~~~

* link:/wiki/Storage[Storage]

endif::wiki[]