I use local nvme to drive the CI workload for the openstack community for the last year or so. It seems to work pretty well. I just created a filesystem (xfs) and mounted it to /var/lib/nova/instances

I moved glance to using my swift backend and it really made the download of the images much faster.

It depends on if the workload is going to handle HA or you are expecting to migrate machines. If the workload is ephemeral or HA can be handled in the app I think local storage is still a very viable option.

Simpler is better IMO

On Wed, Aug 5, 2020 at 7:48 AM Sean Mooney <smooney@redhat.com> wrote:

On Wed, 2020-08-05 at 12:40 +0100, Sean Mooney wrote:
> On Wed, 2020-08-05 at 12:19 +0100, Lee Yarwood wrote:
> > On 05-08-20 05:03:29, Eric K. Miller wrote:
> > > In case this is the answer, I found that in nova.conf, under the
> > > [libvirt] stanza, images_type can be set to "lvm". This looks like it
> > > may do the trick - using the compute node's LVM to provision and mount a
> > > logical volume, for either persistent or ephemeral storage defined in
> > > the flavor.
> > >
> > > Can anyone validate that this is the right approach according to our
> > > needs?
> >
> > I'm not sure if it is given your initial requirements.
> >
> > Do you need full host block devices to be provided to the instance?
> >
> > The LVM imagebackend will just provision LVs on top of the provided VG
> > so there's no direct mapping to a full host block device with this
> > approach.
> >
> > That said there's no real alternative available at the moment.
>
> well one alternitive to nova providing local lvm storage is to use
> the cinder lvm driver but install it on all compute nodes then
> use the cidner InstanceLocalityFilter to ensure the volume is alocated form the host
> the vm is on.
> https://docs.openstack.org/cinder/latest/configuration/block-storage/scheduler-filters.html#instancelocalityfilter
> on drawback to this is that if the if the vm is moved i think you would need to also migrate the cinder volume
> seperatly afterwards.
by the way if you were to take this approch i think there is an nvmeof driver so you can use nvme over rdma
instead of iscsi.
>
> >
> > > Also, I have read about the LVM device filters - which is important to
> > > avoid the host's LVM from seeing the guest's volumes, in case anyone
> > > else finds this message.
> >
> >
> > Yeah that's a common pitfall when using LVM based ephemeral disks that
> > contain additional LVM PVs/VGs/LVs etc. You need to ensure that the host
> > is configured to not scan these LVs in order for their PVs/VGs/LVs etc
> > to remain hidden from the host:
> >
> >
>
>
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/lvm_filters
>
> >
> >
>
>