StorPool CloudStack Integration

CloudStack Overview

Primary and Secondary storage

Primary storage is associated with a cluster or zone, and it stores the virtual disks for all the VMs running on hosts in that cluster/zone.

Secondary storage stores the following:

  • Templates — OS images that can be used to boot VMs and can include additional configuration information, such as installed applications

  • ISO images — disc images containing data or bootable media for operating systems

  • Disk volume snapshots — saved copies of VM data which can be used for data recovery or to create new templates

ROOT and DATA volumes

ROOT volumes correspond to the boot disk of a VM. They are created automatically by CloudStack during VM creation. ROOT volumes are created based on a system disk offering, corresponding to the service offering the user VM is based on. We may change the ROOT volume disk offering but only to another system created disk offering.

DATA volumes correspond to additional disks. These can be created by users and then attached/detached to VMs. DATA volumes are created based on a user-defined disk offering.

Plugin Organization

The StorPool plugin consists of two parts:

KVM hypervisor plugin patch

Source directory: ./apache-cloudstack-4.8.0-src/plugins/hypervisors/kvm

This is due to a bug in Otherwise may have dangling attachments. It is a one line patch: return false in place of true, as the device in question is not iSCSI, thus it is not disconnected (detached) by the iSCSI adaptor.

NB! We need to build and install our own copy of the CloudStack KVM hypervisor plugin on each Agent host.

The issue was fixed upstream on 14 December 2019

StorPool primary storage plugin

Source directory: ./apache-cloudstack-4.8.0-src/plugins/storage/volume

There is one plugin for both the CloudStack management and agents, in the hope that having all the source in one place will ease development and maintenance. The plugin itself though is separated into two mainly independent parts:

  • ./src/com/… directory tree: agent related classes and commands send from management to agent

  • ./src/org/… directory tree: management related classes

The plugin is intended to be self contained and non-intrusive, thus ideally deploying it would consist of only dropping the jar file into the appropriate places. This is the reason why all StorPool related communication (ex. data copying, volume resize) is done with StorPool specific commands even when there is a CloudStack command that does pretty much the same.

Note that for the present the StorPool plugin may only be used for a single primary storage cluster; support for multiple clusters is planned.

Build, Install, Setup


Go to the source directory and run:

mvn -Pdeveloper -DskipTests install

The resulting jar file is located in the target/ subdirectory.

Note: checkstyle errors: before compilation a code style check is performed; if this fails compilation is aborted. In short: no trailing whitespace, indent using 4 spaces, not tabs, comment-out or remove unused imports.

Note: Need to build both the KVM plugin and the StorPool plugin proper.

Build using docker

As alternative in the docker/ directory there are few scripts to create a building environment in a docker container. Follow the corresponding docker/ for further details.


StorPool primary storage plugin

For each CloudStack management host:

scp ./target/cloud-plugin-storage-volume-storpool-{version}.jar {MGMT_HOST}:/usr/share/cloudstack-management/lib/

For each CloudStack agent host:

scp ./target/cloud-plugin-storage-volume-storpool-{version}.jar {AGENT_HOST}:/usr/share/cloudstack-agent/plugins/

Note: CloudStack managements/agents services must be restarted after adding the plugin to the respective directories

Note: Agents should have access to the StorPool management API, since attach and detach operations happens on the agent. This is a CloudStack design issue, can’t do much about it.


Setting up StorPool

Perform the StorPool installation following the StorPool Installation Guide.

Create a template to be used by CloudStack. Must set placeHead, placeAll, placeTail and replication. No need to set default volume size because it is determined by the CloudStack disks and services offering.

Setting up a StorPool PRIMARY storage pool in CloudStack

From the WEB UI, go to Infrastructure -> Primary Storage -> Add Primary Storage

Scope: select Zone-Wide Hypervisor: select KVM Zone: pick appropriate zone. Name: user specified name

Protocol: select SharedMountPoint Path: enter /dev/storpool (required argument, actually not needed in practice).

Provider: select StorPool Managed: leave unchecked (currently ignored) Capacity Bytes: used for accounting purposes only. May be more or less than the actual StorPool template capacity. Capacity IOPS: currently not used (may use for max IOPS limitations on volumes from this pool). URL: enter SP_API_HTTP=address:port;SP_AUTH_TOKEN=token;SP_TEMPLATE=template_name. At present one template can be used for at most one Storage Pool.

SP_API_HTTP - address of StorPool Api SP_AUTH_TOKEN - StorPool’s token SP_TEMPLATE - name of StorPool’s template

Storage Tags: If left blank, the StorPool storage plugin will use the pool name to create a corresponding storage tag. This storage tag may be used later, when defining service or disk offerings.

Plugin Functionality

Plugin Action CloudStack Action management/agent impl. details
Create ROOT volume from ISO create VM from ISO management createVolumeAsync
Create ROOT volume from Template create VM from Template management + agent copyAsync (T => T, T => V)
Create DATA volume create Volume management createVolumeAsync
Attach ROOT/DATA volume start VM (+attach/detach Volume) agent connectPhysicalDisk
Detach ROOT/DATA volume stop VM agent disconnectPhysicalDiskByPath
  Migrate VM agent attach + detach
Delete ROOT volume destroy VM (expunge) management deleteAsync
Delete DATA volume delete Volume (detached) management deleteAsync
Create ROOT/DATA volume snapshot snapshot volume management + agent takeSnapshot + copyAsync (S => S)
Create volume from snapshoot create volume from snapshot management + agent(?) copyAsync (S => V)
Create TEMPLATE from ROOT volume create template from volume management + agent copyAsync (V => T)
Create TEMPLATE from snapshot create template from snapshot SECONDARY STORAGE  
Download volume download volume management + agent copyAsync (V => V)
Revert ROOT/DATA volume to snapshot revert to snapshot management revertSnapshot
(Live) resize ROOT/DATA volume resize volume management + agent resize + StorpoolResizeCmd
Delete SNAPSHOT (ROOT/DATA) delete snapshot management StorpoolSnapshotStrategy
Delete TEMPLATE delete template agent deletePhysicalDisk
migrate VM/volume migrate VM/volume to another storage management/management + agent copyAsync (V => V)
VM snapshot group snapshot of VM's disks management StorpoolVMSnapshotStrategy takeVMSnapshot
revert VM snapshot revert group snapshot of VM's disks management StorpoolVMSnapshotStrategy revertVMSnapshot
delete VM snapshot delete group snapshot of VM's disks management StorpoolVMSnapshotStrategy deleteVMSnapshot
VM vc_policy tag vc_policy tag for all disks attached to VM management StorPoolCreateTagsCmd
delete VM vc_policy tag remove vc_policy tag for all disks attached to VM management StorPoolDeleteTagsCmd

NOTE: When using multicluster for each CloudStack cluster in its settings set the value of StorPool’s SP_CLUSTER_ID in “”.

NOTE: Secondary storage could be bypassed with Configuration setting “” set to true. </br> In this case only snapshots won’t be downloaded to secondary storage.

Creating template from snapshot

If bypass option is enabled

The snapshot exists only on PRIMARY (StorPool) storage. From this snapshot it will be created a template on SECONADRY and PRIMARY storages.

If bypass option is disabled

TODO: Maybe we should not use CloudStack functionality, and to use that one when bypass option is enabled

This is independent of StorPool as snapshots exist on secondary.

Creating ROOT volume from templates

When creating the first volume based on the given template, if snapshot of the template does not exists on StorPool it will be first downloaded (cached) to PRIMARY storage. This is mapped to a StorPool snapshot so, creating consecutive volumes from the same template does not incur additional copying of data to PRIMARY storage.

This cached snapshot is garbage collected when the original template is deleted from CloudStack. This cleanup is done by a background task in CloudStack.

Creating a ROOT volume from an ISO image

We just need to create the volume. The ISO installation is handled by CloudStack.

Creating a DATA volume

DATA volumes are created by CloudStack the first time it is attached to a VM.

Creating volume from snapshot

We use the fact that the snapshot already exists on PRIMARY, so no data is copied. We will copy snapshots from SECONDARY to StorPool PRIMARY, when there is no corresponding StorPool snapshot.

Resizing volumes

We need to send a resize cmd to agent, where the VM the volume is attached to is running, so that the resize is visible by the VM.

Creating snapshots

The snapshot is first created on the PRIMARY storage (i.e. StorPool), then backed-up on SECONDARY storage (tested with NFS secondary) if bypass option is not enabled. The original StorPool snapshot is kept, so that creating volumes from the snapshot does not need to copy the data again to PRIMARY. When the snapshot is deleted from CloudStack so is the corresponding StorPool snapshot.

TODO: Currently snapshots are taken in RAW format. Should we use QCOW2 instead?

Reverting volume to snapshot

It’s handled by StorPool

Migrating volumes to other Storage pools

Tested with storage pools on NFS only.

Virtual Machine Snapshot/Group Snapshot

StorPool supports consistent snapshots of volumes attached to a virtual machine.

BW/IOPS limits

Storage QoS parameter Max IOPS in the disk and service offerings sets the IOPS limit for the StorPool volume. Min IOPS is not supported and the value is ignored.

CloudStack doesn’t support bandwidth limits. A bandwidth limit can be set only through a StorPool template, see below.

BW/IOPS limitations using StorPool templates

If the disk offering (or service offering) are defined with a StorPool template, the volume QoS parameters are always inherited from the template. On disk resize (change disk offering)/ scale VM (change service offering), old IOPS and bandwidth limits of the volume are reset to the values defined in the template. Max IOPS defined in the disk offering (service offering) are ignored in this case.

To define QoS through by StorPool template you have to add disk/service offering resource details with a key SP_TEMPLATE and value the name of the SotoPool template. This could be executed only from the CloudStack CLI (cloudmonkey):

CLI command for the Disk offering:

add resourcedetail resourceid=405c6860-46ad-4d10-a8cc-dad3626bde5f details[0].key=SP_TEMPLATE details[0].value=ssd-limited resourcetype=DiskOffering

CLI command for the Service offering:

add resourcedetail resourceid=ea3c1852-f906-4c78-9ae0-8564bca90cd5 details[0].key=SP_TEMPLATE details[0].value=ssd-limited resourcetype=ServiceOffering