So this brings us back to the original proposal of having separate backing files for Cinder and Nova which Dean thought might take too much space.
Duncan, could you please elaborate on the pain a single volume group is likely to cause for Cinder? Is it a show stopper?
Thank you, Dan 1. https://wiki.archlinux.org/index.php/LVM#LVM_Building_Blocks On 10/21/2014 03:10 PM, Duncan Thomas wrote:
Sharing the vg with cinder is likely to cause some pain testing proposed features cinder reconciling backend with the cinder db. Creating a second vg sharing the same backend pv is easy and avoids all such problems.Duncan ThomasOn Oct 21, 2014 4:07 PM, "Dan Genin" <daniel.ge...@jhuapl.edu <mailto:daniel.ge...@jhuapl.edu>> wrote:Hello, I would like to add to DevStack the ability to stand up Nova with LVM ephemeral storage. Below is a draft of the blueprint describing the proposed feature. Suggestions on architecture, implementation and the blueprint in general are very welcome. Best, Dan ======================== Enable LVM ephemeral storage for Nova ======================== Currently DevStack supports only file based ephemeral storage for Nova, e.g., raw and qcow2. This is an obstacle to Tempest testing of Nova with LVM ephemeral storage, which in the past has been inadvertantly broken (see for example, https://bugs.launchpad.net/nova/+bug/1373962), and to Tempest testing of new features based on LVM ephemeral storage, such as LVM ephemeral storage encryption. To enable Nova to come up with LVM ephemeral storage it must be provided a volume group. Based on an initial discussion with Dean Troyer, this is best achieved by creating a single volume group for all services that potentially need LVM storage; at the moment these are Nova and Cinder. Implementation of this feature will: * move code in lib/cinder/cinder_backends/lvm to lib/lvm with appropriate modifications * rename the Cinder volume group to something generic, e.g., devstack-vg * modify the Cinder initialization and cleanup code appropriately to use the new volume group * initialize the volume group in stack.sh, shortly before services are launched * cleanup the volume group in unstack.sh after the services have been shutdown The question of how large to make the common Nova-Cinder volume group in order to enable LVM ephemeral Tempest testing will have to be explored. Although, given the tiny instance disks used in Nova Tempest tests, the current Cinder volume group size may already be adequate. No new configuration options will be necessary, assuming the volume group size will not be made configurable. _______________________________________________ OpenStack-dev mailing list OpenStackemail@example.com <mailto:OpenStackfirstname.lastname@example.org> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev _______________________________________________ OpenStack-dev mailing list OpenStackemail@example.com http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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