The Block LVM Datastore

Overview

The Block LVM datastore driver provides OpenNebula with the possibility of using LVM volumes instead of plain files to hold the Virtual Images.

It is assumed that the OpenNebula hosts using this datastore will be configured with CLVM, therefore modifying the OpenNebula Volume Group in one host will reflect in the others. There is a special list of hosts (BRIDGE_LIST) which belong to the LVM cluster, that will be the ones OpenNebula uses to speak to when doing LVM operations.

Development

To contribute bug patches or new features, you can use the github Pull Request model. It is assumed that code and documentation are contributed under the Apache License 2.0.

More info:

• How to Contribute
• Support: OpenNebula user forum
• Development: OpenNebula developers forum
• Issues Tracking: Github issues (https://github.com/OpenNebula/addon-lvm/issues)

Authors

• Leader: Javier Fontan (jfontan@opennebula.org)

Compatibility

This add-on is compatible with OpenNebula >= 6.0.

Requirements

OpenNebula Front-end

• Password-less ssh access to an OpenNebula LVM-enabled host.

OpenNebula LVM Hosts

LVM must be available in the Hosts. The oneadmin user should be able to execute several LVM related commands with sudo passwordlessly.

• Password-less sudo permission for: lvremove, lvcreate, lvs, vgdisplay.
• LVM2
• oneadmin needs to belong to the disk group (for KVM).

Configuration

Configuring the System Datastore

To use LVM drivers, the system datastore will work both with shared or as ssh. This sytem datastore will hold only the symbolic links to the block devices, so it will not take much space. See more details on the System Datastore Guide <system_ds>

It will also be used to hold context images and Disks created on the fly, they will be created as regular files.

Configuring Block LVM Datastores

The first step to create a LVM datastore is to set up a template file for it.

The specific attributes for this datastore driver are listed in the following table, you will also need to complete with the common datastore attributes <sm_common_attributes>:

Attribute	Description
TYPE	Must be IMAGE_DS
DS_MAD	Must be lvm
TM_MAD	Must be lvm
DISK_TYPE	Must be BLOCK
VG_NAME	The LVM volume group name. Defaults to vg-one
BRIDGE_LIST	Mandatory space separated list of LVM frontends.
MKFS_EXT_OPTS	Optional mkfs.ext command line arguments. E.g. -b 4096 -E stride=128,stripe-width=256
MKFS_XFS_OPTS	Optional mkfs.xfs command line arguments. E.g. -b size=4096 -d su=512K,sw=2

For example, the following examples illustrates the creation of an LVM datastore using a configuration file. In this case we will use the host host01 as one of our OpenNebula LVM-enabled hosts.

> cat ds.conf
NAME = production
TYPE = IMAGE_DS
DS_MAD = lvm
TM_MAD = lvm
DISK_TYPE = BLOCK
VG_NAME = vg-one
BRIDGE_LIST = "host01 host02"

> onedatastore create ds.conf
ID: 100

> onedatastore list
  ID NAME            CLUSTERS IMAGES TYPE   DS     TM

 100 production      0        0      img    lvm    lvm
   1 default         0        0      img    fs     ssh
   0 system          0        0      sys    -      ssh

The DS and TM MAD can be changed later using the onedatastore update command. You can check more details of the datastore by issuing the onedatastore show command.

warning

Note that datastores are not associated to any cluster by default, and they are supposed to be accessible by every single host. If you need to configure datastores for just a subset of the hosts take a look to the Cluster guide <cluster_guide>.

After creating a new datastore the LN_TARGET and CLONE_TARGET parameters will be added to the template. These values should not be changed since they define the datastore behaviour. The default values for these parameters are defined in oned.conf <oned_conf> for each driver.

Host Configuration

The hosts must have LVM2 and have the Volume-Group used in the VG_NAME attributed of the datastore template. CLVM must also be installed and active accross all the hosts that use this datastore.

It's also required to have password-less sudo permission for: lvremove, lvcreate, lvs, vgdisplay.

Tuning & Extending

System administrators and integrators are encouraged to modify these drivers in order to integrate them with their datacenter:

Under /var/lib/one/remotes/:

• datastore/lvm/lvm.conf: Default values for LVM parameters
  • VG_NAME: Default volume group
  • DEFAULT_SIZE: Default size of the snapshots
• datastore/lvm/cp: Registers a new image. Creates a new logical volume in LVM.
• datastore/lvm/mkfs: Makes a new empty image. Creates a new logical volume in LVM.
• datastore/lvm/rm: Removes the LVM logical volume.
• tm/lvm/ln: Links to the LVM logical volume.
• tm/lvm/clone: Clones the image by creating a snapshot.
• tm/lvm/mvds: Saves the image in a new LV for SAVE_AS.