Instance resource quota not observed for non-ephemeral storage

Bug #1445637 reported by Tony Walker on 2015-04-17
This bug affects 1 person
Affects Status Importance Assigned to Milestone
OpenStack Compute (nova)

Bug Description

I'm using a nova built from stable/kilo and trying to implement instance IO resource quotas for disk as per

While this works when building an instance from ephemeral storage, it does not when booting from a bootable cinder volume. I realize I can implement this using cinder quota but I want to apply the same settings in nova regardless of the underlying disk.

Steps to produce:

nova flavor-create iolimited 1 8192 64 4
nova flavor-key 1 set quota:disk_read_iops_sec=10000
Boot an instance using the above flavor
Guest XML is missing <iotune> entries

Expected result:
      <target dev='vda' bus='virtio'/>

This relates somewhat to but that case is purely hit when booting from RBD-backed ephemeral storage.

Essentially, for non-ephemeral disks, a call is made to _get_volume_config() which creates a generic LibvirtConfigGuestDisk object but no further processing is done to add extra-specs (if any).

I've essentially copied the disk_qos() method from the associated code review ( to implement my own patch (attached).

Tony Walker (tony-walker-h) wrote :
Changed in nova:
importance: Undecided → Low
status: New → Confirmed
tags: added: quotas
tags: added: libvirt
Changed in nova:
assignee: nobody → lyanchih (lyanchih)

Fix proposed to branch: master

Changed in nova:
status: Confirmed → In Progress

Change abandoned by lyanchih (<email address hidden>) on branch: master

Chung Chih, Hung (lyanchih) wrote :

Cinder client had offer qos command. Those instance quota settings of non-emphemeral disk should be set via cinder cli instead of inherit from instance's flavor.

Changed in nova:
status: In Progress → Invalid
Tony Walker (tony-walker-h) wrote :

I'm aware of the ability to do this via cinder quota but why force this as the only option? By applying this via host aggregates I can generically control users rather than having to individually manage their instances on a per-volume basis. Given this is done for ephemeral volumes can you explain why a solution in nova will be abandoned?

Chung Chih, Hung (lyanchih) wrote :

I'm sorry for I was too hurry to change into invalid.
Originally I was thought those non-ephemeral disk was managed by cinder, those settings should dependent on it.
And even you assign higher value, the rate was still limit by cinder. Then you can't observed the real rate.
But I also thought flavor was hardware template, its settings should also apply.
Maybe we could select the minimum quota value between cinder or flavor settings.

Changed in nova:
status: Invalid → In Progress
Tony Walker (tony-walker-h) wrote :

No problem - just wanted to understand. Thanks for reconsidering. It would certainly be helpful to accept limits from Nova only (in the case that cinder quotas aren't being set).

@lyanchich, are you still working on this ? Also, changing status to "new" as the existing patch has -2 by core reviewer.

Changed in nova:
status: In Progress → New
Changed in nova:
status: New → Confirmed
assignee: Chung Chih, Hung (lyanchih) → nobody

In review [1] it was figured out that this is a feature request (=>"wishlist"). The effort is driven by the bp [2] (=> "Opinion"). No need for this bug report anymore.


Changed in nova:
status: Confirmed → Opinion
importance: Low → Wishlist

Change abandoned by Michael Still (<email address hidden>) on branch: master
Reason: This code hasn't been updated in a long time, and is in merge conflict. I am going to abandon this review, but feel free to restore it if you're still working on this.

Prateek Arora (parora) on 2016-09-13
Changed in nova:
assignee: nobody → Prateek Arora (parora)
Matt Riedemann (mriedem) wrote :

I don't think this is orchestration/proxy work that we want Nova to do when creating a volume during the boot from volume scenario. There is agreement, however, to allow passing a volume type when booting an instance for the BFV scenario and the volume type can have the QoS specs in it, see:

-- mriedem 20160920

Prateek Arora (parora) wrote :

Removing myself as assignee as this is something we won't incorporate in nova.

Changed in nova:
assignee: Prateek Arora (parora) → nobody
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