Adding iSCSI backend store driver for glance

Registered by Zhi Yan Liu

This blueprint has been superseded. See the newer blueprint "Adding a store driver to allow Cinder as a block storage backend for Glance" for updated plans.

Under this change Glance can expose any iSCSI back-end volume (LUN) as an image (also include Cinder volume). Client can retrieve it through single or multiple path. According to this, nova-compute can use the iSCSI (through single or multiple iSCSI path) plus dm-snapshot method to implement base image and its COW mechanism, this will decrease base image creating time and effective improve provisioning performance.

Blueprint information

Vish Ishaya
Zhi Yan Liu
Needs approval
Zhi Yan Liu
Series goal:
Good progress
Milestone target:
Started by
Zhi Yan Liu
Completed by
Mark Washenberger

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Addressed by:
    Adding iSCSI backend store driver

I would love it if we changed OpenStack's whole semantic from "Nova boots Images or Volumes"
to "Nova Boots Volumes" AND "A Volume may be preloaded with data from an Image." Then, Nova would always have access to an underlying Volume for an instance for fast snapshots and cloning.

However, if we cannot make so great a change quickly enough, I would at least like to focus on synergy with Cinder by making a cinder driver for image data rather than directly using iscsi. So I'm going to mark this as superseded by your other blueprint "glance-cinder-driver".

Mark Wash, I'd like post some previous comments here, which talked with John Griffith and Brian Waldon.
I consider this store driver is not as close related with Cinder as you think. I have two comments for this driver:

1. This iSCSI driver is a common driver to allow Glance
export any back-end LUN/volume as an image. Of cause, you can expose
Cinder iscsi volume via it, but there's no limition, it's a common
implmentation for any LUN/volume back-end.
This common iSCSI driver can support multi-path accessing, but Cinder
driver will not now since current Cinder iscsi volume based LVM does not
support selective replication or full replication on cinder-volume nodes.
This dirver can be used to access traditional filer/storage. For now, I think
this should like HTTP store. So I consider we can land this store driver down.

2. Of cause, I agree with you, we have a driver for swift as a object
storage back-end for Glance, so make a block storage back-end is make
sense to me, that is Cinder (blueprint "glance-cinder-driver").

Based on discussions at the summit, it seems like most folks (including John Lindeman who as I understand is the expert on the multipath / dm-snapshot use case at IBM) want to go the route of hiding iscsi details beneath cinder.


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