cloudstack/plugins/storage/volume/storpool/README.md

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-4.17-src/plugins/hypervisors/kvm

StorPool primary storage plugin

Source directory: ./apache-cloudstack-4.17.0-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

Build

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.

Install

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.

Setup

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

NOTE: You can use the alternative format option for the URL - storpool://{SP_AUTH_TOKEN}@{SP_API_HTTP}:{SP_API_HTTP_PORT}/{SP_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 snapshot	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 "sp.cluster.id".

NOTE: Secondary storage could be bypassed with Configuration setting "sp.bypass.secondary.storage" set to true.
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 SECONDARY.

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 successive 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.

Currently snapshots are taken in RAW format.

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 limitations

Max IOPS are kept in StorPool's volumes with the help of custom service offerings, by adding IOPS limits to the corresponding system disk offering.

CloudStack has no way to specify max BW. Do they want to be able to specify max BW only is sufficient.

StorPool provides the ‘storpool_qos’ service (QoS user guide) that tracks and configures the storage tier for all volumes based on a specifically provided qc tag specifying the storage tier for each volume.

To manage the QoS limits with a qc tag, you have to add a qc tag resource detail to each disk offering to which a tier should be applied, with a key SP_QOSCLASS and the value from the configuration file for the storpool_qos service:

add resourcedetail resourceid={diskofferingid} details[0].key=SP_QOSCLASS details[0].value={the name of the tier from the config} resourcetype=DiskOffering

To change the tier via CloudStack, you can use the CloudStack API call changeOfferingForVolume. The size is required, but the user could use the current volume size. Example:

change offeringforvolume id={The UUID of the Volume} diskofferingid={The UUID of the disk offering} size={The current or a new size for the volume}

Users who were using the offerings to change the StorPool template via the SP_TEMPLATE detail, will continue to have this functionality but should use changeOfferingForVolume API call instead of:

• resizeVolume API call for DATA disk
• scaleVirtualMachine API call for ROOT disk

If the disk offering has both SP_TEMPLATE and SP_QOSCLASS defined, the SP_QOSCLASS detail will be prioritised, setting the volume’s QoS using the respective ‘qc’ tag value. In case the QoS for a volume is changed manually, the ‘storpool_qos’ service will automatically reset the QoS limits following the ‘qc’ tag value once per minute.

Usage

Creating Disk Offering for each tier.

Go to Service Offerings > Disk Offering > Add disk offering.

Add disk offering detail with API call in CloudStack CLI.

add resourcedetail resourcetype=diskoffering resourceid=$UUID details[0].key=SP_QOSCLASS details[0].value=$Tier Name

Creating VM with QoS

Deploy virtual machine: Go to Compute> Instances> Add Instances.

• For the ROOT volume, choose the option Override disk offering. This will set the required qc tag from the disk offering (DO) detail.

Creating DATA disk with QoS

• Create volume via GUI/CLI and choose a disk offering which has the required SP_QOSCLASS detail

To update the tier of a ROOT/DATA volume go to Storage> Volumes and select the Volume and click on the Change disk offering for the volume in the upper right corner.

Supported operations for Volume encryption

Supported Virtual machine operations - live migration of VM to another host, virtual machine snapshots (group snapshot without memory), revert VM snapshot, delete VM snapshot

Supported Volume operations - attach/detach volume, live migrate volume between two StorPool primary storages, volume snapshot, delete snapshot, revert snapshot

Note: volume snapshot are allowed only when sp.bypass.secondary.storage is set to true. This means that the snapshots are not backed up to secondary storage