[openstack-dev] [nova] Rocky PTG summary - nova/cinder

melanie witt melwittt at gmail.com
Wed Mar 14 23:39:27 UTC 2018

Hello all,

Here’s the PTG summary etherpad [0] for the nova/cinder session from the PTG, also included as a plain text export on this email.


[0] https://etherpad.openstack.org/p/nova-ptg-rocky-cinder-summary

*Nova/Cinder: Rocky PTG Summary

https://etherpad.openstack.org/p/nova-ptg-rocky L63

*Key topics

  * New attach flow fixes and multi-attach
    * Attach mode
    * Swap volume with two read/write attachments
    * SHELVED_OFFLOADED and 'in-use' state in old attach flow
    * Server multi-create with attaching to the same volume fails
  * Data migration for old-style attachments
  * Volume replication for in-use volumes
  * Object-ifying os-brick connection_info
  * Formatting blank encrypted volumes during creation on the cinder side
  * Volume detail show reveals the attached compute hostname for non-admins
  * Bulk volume create/attach

*Agreements and decisions

  * To handle attach mode for a multi-attach volume to several instances, we will change the compute API to allow the user to pass the attach mode so we can pass it through to cinder
    * The second attachment is going to be read/write by default and if the user wants read-only, they have to specify it
    * Spec: https://review.openstack.org/#/c/552078/
  * Swap volume with two read/write attachments could definitely corrupt data. However, the cinder API doesn't allow retype/migration of in-use multi-attach volumes, so this isn't a problem right now
  * It would be reasonable to fix SHELVED_OFFLOADED to leave the volume in 'reserved' state instead of 'in-use', but it's low priority
  * The bug with server multi-create and multi-attach will be fixed on the cinder side and we'll add a new compute API microversion to leverage the cinder fix
    * Spec: https://review.openstack.org/#/c/552078/
  * We'll migrate old-style attachments on-the-fly when a change is made to a volume, such as a migration. For the rest, we'll migrate old-style attachments on compute startup to new-style attachments
    * Compute startup data migration patch: https://review.openstack.org/#/c/549130/
  * For volume replication of in-use volumes, on the cinder side, we'll need a prototype and spec, and drivers will need to indicate the type of replication and what recovery on the nova side needs to be. On the nova side, we'll need a new API microversion for the os-server-external-events change (like extended volume)
    * Owner: jgriffith
  * On the possibility of object-ifying connection_info in os-brick, it would be best to defer it until nova/neutron have worked out vif negotiation using os-vif
    * lyarwood asked to restore https://review.openstack.org/#/c/269867/
  * On formatting blank encrypted volumes during creation, it sounded like we had agreement to fix it on the cinder side as they already have code for it. Need to double-check with the cinder team to make sure
  * For volume detail show revealing the attached compute hostname for non-admins, cinder will make a change to add a policy to not display the compute hostname for non-admins
    * Note: this doesn't impact nova, but it might impact glance.
  * On bulk volume create/attach, it will be up to cinder to decide whether they will want to implement bulk create. In nova, we are not going to support bulk attach as that's a job better done by an orchestration system like Heat
    * Note: Cinder team agreed to not support bulk create: https://wiki.openstack.org/wiki/CinderRockyPTGSummary#Bulk_Volume_Create.2FAttach

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