Nova using ephemeral storage with cinder

Registered by Tobias Engelbert on 2014-04-30

As a cloud provider I would like to manage all the storage related activities through one entity: cinder. The ambition is that cinder could decide what back-end to use based on SLAs (e.g low-performing or high-performing but also persistent or ephemeral). Those SLAs could come from the tenant or from the infrastructure and thus, cinder shall serve the needs for nova's ephemeral storage, glance image storage and cinder block storage.
As there is development ongoing in glance to use cinder as image backend, we have to address the usage in nova to use ephemeral storage with cinder as backend. The workaround using bootable volumes is not seen as a future proof solution, because it requires explicit calls to Cinder API and therefor additional burden on the user as just calling nova is not sufficient.
Proposal
- VM boot requested by the tenant
- Nova tries to find an "ephemeral" volume for the VM
- Today nova will use the local disk. This blueprint suggests to change nova to be able to use a cinder volume as ephemeral storage instead of local disk.
Related Topic:
https://blueprints.launchpad.net/nova/+spec/nova-ephemeral-storage-with-cinder

Blueprint information

Status:
Not started
Approver:
None
Priority:
Undefined
Drafter:
None
Direction:
Needs approval
Assignee:
John Griffith
Definition:
New
Series goal:
None
Implementation:
Unknown
Milestone target:
None

Related branches

Sprints

Whiteboard

Gerrit topic: https://review.openstack.org/#q,topic:bp/nova-ephemeral-cinder,n,z

Addressed by: https://review.openstack.org/91321
    Implements: blueprint nova-ephemeral-cinder

Gerrit topic: https://review.openstack.org/#q,topic:bp/to,n,z

This came up again at the Pike PTG, and John Griffith was interested in working on this.

http://lists.openstack.org/pipermail/openstack-dev/2017-February/113063.html

-- mriedem 20170306

Alternative (rejected): https://blueprints.launchpad.net/nova/+spec/create-bdm-from-flavor-extra-specs

We are now past the spec freeze for the Pike release so I'm untargeting this from Pike. We do have a session planned for the Forum at the Boston summit for this idea:

https://www.openstack.org/summit/boston-2017/summit-schedule/events/18738/using-cinder-for-nova-ephemeral-storage-backend

So we should gather feedback and requirements from operators so we can start building a spec and plan for doing this in Queens. -- mriedem 20170418

(?)

Work Items

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