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 Thomas On Oct 21, 2014 4:07 PM, "Dan Genin" <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 > OpenStackfirstname.lastname@example.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > >
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