StorPool QoS class configuration

This document describes the configuration options for setting StorPool QoS classes in OpenNebula with the StorPool addon.

Installation

The function to update the VM and enforce the policy is part of the VolumeCare helper script.

QoS class priority order

The StorPool addon uses a hierarchical approach to determine which QoS class to apply to a volume. The priority order (from lowest to highest) is:

  1. Global default (DEFAULT_QOSCLASS)

  2. Datastore-level (SP_QOSCLASS)

  3. Image-level (for persistent images) (SP_QOSCLASS)

  4. VM-level (SP_QOSCLASS)

  5. Per-disk configuration within VM (SP_QOSCLASS with disk ID specifiers)

The highest priority setting that applies to a specific disk will be used.

Note: for the persistent images when there is a Image-level QoS class set, the VM-level classification does not override it. Only the fine-grained per-disk configuration overrides them.

The following table shows the priorities:

TYPE

DEFAULT_QOSCLASS

IMAGE SP_QOSCLASS

IMAGE DS SP_QOSCLASS

SYSTEM DS SP_QOSCLASS

VM SP_QOSCLASS

VM DISK SP_QOSCLASS

PERSISTANT

<

<!

<?

<?

<?

<

NON-PERS

<

-

-

<

<

<

CDROM

<

-

-

<

<

<

VOLATILE

<

-

-

<

<

<

SAVE-AS

<

-

<

-

-

-

DS_CLONE

<

<!

<?

-

-

-

Where:

Label

Description

‘<’

tag available

‘<!’

a “prioritized” tag

‘<?’

tag overriden by a “prioritized” one

‘-’

not applicable

Setting QoS tags

Note: QoS tag names must not contain colon : or semicolon ; as these are reserved symbols used for configuration parsing!

Global QoS class tag (lowest priority)

Set in /var/lib/one/remotes/addon-storpoolrc:

DEFAULT_QOSCLASS=QoS_class_tag_name

This will be applied to all VM disks and images unless overridden by a higher priority setting.

Datastore QoS class tag

Set in the datastore template:

SP_QOSCLASS=QoS_class_tag_name

This applies to all volumes in the specific datastore unless overridden.

Image QoS class tag

For persistent images, add to the image template:

SP_QOSCLASS=QoS_class_tag_name

VM-Level QoS class tag

Set in the VM template:

SP_QOSCLASS=QoS_class_tag_name

This applies to all [*] VM disks unless overridden by Persistent Image QoS tag or per-disk settings.

Per-Disk QoS class tag (highest priority)

This an extension to the VM-level QoS class tag. For fine-grained control, use a semicolon-separated list in the VM template:

Format: [default_qos];[disk_id]:[qos_name];[disk_id]:[qos_name]...

SP_QOSCLASS=defaultVMQosTagName;2:QosTagNameForDiskId2;4:QosTagNameForDiskId4

In this example:

  • Disks with ID 2 and 4 will use their specific QoS classes.

  • All other disks will use defaultVMQosTagName or persistentImageQoSTagName if the disk is a persistent image.

If you only want to specify certain disks without a VM-wide default:

SP_QOSCLASS=0:QosTagNameForDiskId0;3:QosTagNameForDiskId3

In this case:

  • Disks with ID 0 and 3 will use their specific QoS classes.

  • All other disks will fall back to image, datastore or global defaults.

How QoS classes are applied

When a VM is created or modified, the addon determines the appropriate QoS class for the VM and its disks based on the priority order above, and applies it as a tag to the StorPool volume. The QoS policies defined in StorPool are then automatically applied to the volumes by the storpool_qos service.

When a VM disk is saved as an Image to an Image Datastore it is inheriting the SP_QOSCLAS defined for the datastore, or the global DEFAULT_QOSCLASS variable. Note that when a DEFAULT_QOSCLASS is not defined, the driver could pick SP_QOSCLASS from the definition the Image used for the VM disk.

When a VM is terminated, the Persistent disk Images are tagged following the standard priority.

Debugging

To troubleshoot QoS class assignment issues, check the OS logs (syslog or journal) for output from the debug_sp_qosclass function, which shows which QoS class was selected.

To enable debug logging, set DEBUG_SP_QOSCLASS=1 in /var/lib/one/remotes/addon-storpoolrc