As a side-note, the new AWS flavors seem to indicate that the Amazon
infrastructure is moving to all ECS volumes (and all flash, possibly), both
ephemeral and not. This makes sense, as fewer code paths and less
interoperability complexity is a good thing.

That the same balance of concerns should apply in OpenStack, seems likely.




On Tue, Oct 21, 2014 at 7:59 AM, 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
> OpenStack-dev@lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>
>
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