add warning about over-provisioning

[pve-docs.git] / pvesm.adoc

[[chapter-storage]]
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NAME
----

pvesm - Proxmox VE Storage Manager


SYNOPSYS
--------

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DESCRIPTION
-----------
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{pve} Storage
=============
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The {pve} storage model is very flexible. Virtual machine images
can either be stored on one or several local storages, or on shared
storage like NFS or iSCSI (NAS, SAN). There are no limits, and you may
configure as many storage pools as you like. You can use all
storage technologies available for Debian Linux.

One major benefit of storing VMs on shared storage is the ability to
live-migrate running machines without any downtime, as all nodes in
the cluster have direct access to VM disk images. There is no need to
copy VM image data, so live migration is very fast in that case.

The storage library (package 'libpve-storage-perl') uses a flexible
plugin system to provide a common interface to all storage types. This
can be easily adopted to include further storage types in future.


Storage Types
-------------

There are basically two different classes of storage types:

Block level storage::

Allows to store large 'raw' images. It is usually not possible to store
other files (ISO, backups, ..) on such storage types. Most modern
block level storage implementations support snapshots and clones.
RADOS, Sheepdog and DRBD are distributed systems, replicating storage
data to different nodes.

File level storage::

They allow access to a full featured (POSIX) file system. They are
more flexible, and allows you to store any content type. ZFS is
probably the most advanced system, and it has full support for
snapshots and clones.


.Available storage types
[width="100%",cols="<d,1*m,4*d",options="header"]
|===========================================================
|Description    |PVE type    |Level |Shared|Snapshots|Stable
|ZFS (local)    |zfspool     |file  |no    |yes      |yes
|Directory      |dir         |file  |no    |no       |yes
|NFS            |nfs         |file  |yes   |no       |yes
|GlusterFS      |glusterfs   |file  |yes   |no       |yes
|LVM            |lvm         |block |no    |no       |yes
|LVM-thin       |lvmthin     |block |no    |yes      |yes
|iSCSI/kernel   |iscsi       |block |yes   |no       |yes
|iSCSI/libiscsi |iscsidirect |block |yes   |no       |yes
|Ceph/RBD       |rbd         |block |yes   |yes      |yes
|Sheepdog       |sheepdog    |block |yes   |yes      |beta
|DRBD9          |drbd        |block |yes   |yes      |beta
|ZFS over iSCSI |zfs         |block |yes   |yes      |yes
|=========================================================

TIP: It is possible to use LVM on top of an iSCSI storage. That way
you get a 'shared' LVM storage.

Thin provisioning
~~~~~~~~~~~~~~~~~

A number of storages, and the Qemu image format `qcow2`, support _thin
provisioning_.  With thin provisioning activated, only the blocks that
the guest system actually use will be written to the storage.

Say for instance you create a VM with a 32GB hard disk, and after
installing the guest system OS, the root filesystem of the VM contains
3 GB of data.  In that case only 3GB are written to the storage, even
if the guest VM sees a 32GB hard drive. In this way thin provisioning
allows you to create disk images which are larger than the currently
available storage blocks. You can create large disk images for your
VMs, and when the need arises, add more disks to your storage without
resizing the VMs filesystems.

All storage types which have the 'Snapshots' feature also support thin
provisioning.

CAUTION: If a storage runs full, all guests using volumes on that
storage receives IO error. This can cause file system inconsistencies
and may corrupt your data. So it is advisable to avoid
over-provisioning of your storage resources, or carefully observe
free space to avoid such conditions.

Storage Configuration
---------------------

All {pve} related storage configuration is stored within a single text
file at '/etc/pve/storage.cfg'. As this file is within '/etc/pve/', it
gets automatically distributed to all cluster nodes. So all nodes
share the same storage configuration.

Sharing storage configuration make perfect sense for shared storage,
because the same 'shared' storage is accessible from all nodes. But is
also useful for local storage types. In this case such local storage
is available on all nodes, but it is physically different and can have
totally different content.

Storage Pools
~~~~~~~~~~~~~

Each storage pool has a `<type>`, and is uniquely identified by its `<STORAGE_ID>`. A pool configuration looks like this:

----
<type>: <STORAGE_ID>
	<property> <value>
	<property> <value>
	...
----

NOTE: There is one special local storage pool named `local`. It refers to
the directory '/var/lib/vz' and is automatically generated at installation
time.

The `<type>: <STORAGE_ID>` line starts the pool definition, which is then
followed by a list of properties. Most properties have values, but some of
them come with reasonable default. In that case you can omit the value.

.Default storage configuration ('/etc/pve/storage.cfg')
----
dir: local
	path /var/lib/vz
	content iso,vztmpl,backup

lvmthin: local-lvm
	thinpool data
	vgname pve
	content rootdir,images
----

Common Storage Properties
~~~~~~~~~~~~~~~~~~~~~~~~~

A few storage properties are common among different storage types.

nodes::

List of cluster node names where this storage is
usable/accessible. One can use this property to restrict storage
access to a limited set of nodes.

content::

A storage can support several content types, for example virtual disk
images, cdrom iso images, container templates or container root
directories. Not all storage types support all content types. One can set
this property to select for what this storage is used for.

images:::

KVM-Qemu VM images.

rootdir:::

Allow to store container data.

vztmpl:::

Container templates.

backup:::

Backup files ('vzdump').

iso:::

ISO images

shared::

Mark storage as shared.

disable::

You can use this flag to disable the storage completely.

maxfiles::

Maximal number of backup files per VM. Use `0` for unlimted.

format::

Default image format (`raw|qcow2|vmdk`)


WARNING: It is not advisable to use the same storage pool on different
{pve} clusters. Some storage operation need exclusive access to the
storage, so proper locking is required. While this is implemented
within a cluster, it does not work between different clusters.


Volumes
-------

We use a special notation to address storage data. When you allocate
data from a storage pool, it returns such a volume identifier. A volume
is identified by the `<STORAGE_ID>`, followed by a storage type
dependent volume name, separated by colon. A valid `<VOLUME_ID>` looks
like:

 local:230/example-image.raw

 local:iso/debian-501-amd64-netinst.iso

 local:vztmpl/debian-5.0-joomla_1.5.9-1_i386.tar.gz

 iscsi-storage:0.0.2.scsi-14f504e46494c4500494b5042546d2d646744372d31616d61

To get the filesystem path for a `<VOLUME_ID>` use:

 pvesm path <VOLUME_ID>

Volume Ownership
~~~~~~~~~~~~~~~~

There exists an ownership relation for 'image' type volumes. Each such
volume is owned by a VM or Container. For example volume
`local:230/example-image.raw` is owned by VM 230. Most storage
backends encodes this ownership information into the volume name.

When you remove a VM or Container, the system also removes all
associated volumes which are owned by that VM or Container.


Using the Command Line Interface
--------------------------------

It is recommended to familiarize yourself with the concept behind storage
pools and volume identifiers, but in real life, you are not forced to do any
of those low level operations on the command line. Normally,
allocation and removal of volumes is done by the VM and Container
management tools.

Nevertheless, there is a command line tool called 'pvesm' ({pve}
storage manager), which is able to perform common storage management
tasks.


Examples
~~~~~~~~

Add storage pools

 pvesm add <TYPE> <STORAGE_ID> <OPTIONS>
 pvesm add dir <STORAGE_ID> --path <PATH>
 pvesm add nfs <STORAGE_ID> --path <PATH> --server <SERVER> --export <EXPORT>
 pvesm add lvm <STORAGE_ID> --vgname <VGNAME>
 pvesm add iscsi <STORAGE_ID> --portal <HOST[:PORT]> --target <TARGET>

Disable storage pools

 pvesm set <STORAGE_ID> --disable 1

Enable storage pools

 pvesm set <STORAGE_ID> --disable 0

Change/set storage options

 pvesm set <STORAGE_ID> <OPTIONS>
 pvesm set <STORAGE_ID> --shared 1
 pvesm set local --format qcow2
 pvesm set <STORAGE_ID> --content iso

Remove storage pools. This does not delete any data, and does not
disconnect or unmount anything. It just removes the storage
configuration.

 pvesm remove <STORAGE_ID>

Allocate volumes

 pvesm alloc <STORAGE_ID> <VMID> <name> <size> [--format <raw|qcow2>]

Allocate a 4G volume in local storage. The name is auto-generated if
you pass an empty string as `<name>`

 pvesm alloc local <VMID> '' 4G

Free volumes 

 pvesm free <VOLUME_ID>

WARNING: This really destroys all volume data.

List storage status

 pvesm status

List storage contents

 pvesm list <STORAGE_ID> [--vmid <VMID>]

List volumes allocated by VMID

 pvesm list <STORAGE_ID> --vmid <VMID>

List iso images

 pvesm list <STORAGE_ID> --iso

List container templates

 pvesm list <STORAGE_ID> --vztmpl

Show filesystem path for a volume

 pvesm path <VOLUME_ID>

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See Also
--------

* link:/index.php/Storage:_Directory[Storage: Directory]

* link:/index.php/Storage:_GlusterFS[Storage: GlusterFS]

* link:/index.php/Storage:_User_Mode_iSCSI[Storage: User Mode iSCSI]

* link:/index.php/Storage:_iSCSI[Storage: iSCSI]

* link:/index.php/Storage:_LVM[Storage: LVM]

* link:/index.php/Storage:_LVM_Thin[Storage: LVM Thin]

* link:/index.php/Storage:_NFS[Storage: NFS]

* link:/index.php/Storage:_RBD[Storage: RBD]

* link:/index.php/Storage:_ZFS[Storage: ZFS]


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// backend documentation

include::pve-storage-dir.adoc[]

include::pve-storage-nfs.adoc[]

include::pve-storage-glusterfs.adoc[]

include::pve-storage-zfspool.adoc[]

include::pve-storage-lvm.adoc[]

include::pve-storage-lvmthin.adoc[]

include::pve-storage-iscsi.adoc[]

include::pve-storage-iscsidirect.adoc[]

include::pve-storage-rbd.adoc[]



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