Open Stack

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.genin at 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
> OpenStack-dev at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstack.org/pipermail/openstack-dev/attachments/20141021/5c94ab6f/attachment.html>