Open Stack

The difference between "sda" and "vdb" is the disk controller:

In case of first disk: <target dev='sda' bus='scsi'/>
Disk added via virsh: <target dev='vdb' bus='virtio'/>

You can set OS image properties to achieve this setup and then re-create the VM:

hw_disk_bus=|virtio and remove property "|||hw_scsi_model"| |
Now to update properties of existing images: https://docs.openstack.org/glance/latest/admin/manage-images.html
You can read more about image properties here: https://docs.openstack.org/glance/latest/admin/useful-image-properties.html

On 14.08.2023 14:37, Jan Wasilewski wrote:
> Hi,
>
> I was conducting another round of tests, which is not a complete 
> solution for the OpenStack platform itself. However, it served as a 
> clever method to assess real NVMe performance within a virtual machine 
> (VM). I decided to attach a full NVMe disk to a VM as "vdb" and assess 
> the performance there. Interestingly, I managed to achieve 
> approximately 80,000 IOPS, signifying a significant improvement. 
> Nevertheless, it's worth noting that this approach may not be directly 
> applicable to my solution, as the root disk configured in the flavor 
> must be labeled as "vda". Regardless, I wanted to present this as a 
> reference to demonstrate that achieving higher IOPS is indeed 
> possible. With collaborative efforts, perhaps similar results can be 
> attained for "vda" disks in fully OpenStack-managed VMs. The disk was 
> added using the following "virsh" command: "virsh attach-disk 
> instance-000034ba /dev/nvme1n1p1 vdb". Additional results, as well as 
> the "dumpxml" output for this VM, are presented in references [1] and [2].
>
> While achieving 80,000 IOPS is satisfactory for me, I also conducted 
> separate tests with a VM that was entirely managed by Libvirt, without 
> involving OpenStack. The VM was set up using the following command: 
> "virt-install --virt-type=kvm --name=local-ubuntu --vcpus=2 
> --memory=4096 --disk 
> path=/var/lib/nova/instances/test/disk,format=qcow2 --import --network 
> default --graphics none"
>
> In this case, the OS image used was identical to the one employed in 
> my full OpenStack test. The procedure for attaching a "vdb" drive was 
> replicated exactly as it was for my OpenStack VM. The outcome of these 
> tests is quite surprising. I was able to achieve around 130,000 IOPS, 
> despite the configuration being nearly identical. This discrepancy is 
> perplexing and suggests that there might be an issue with the Nova 
> component itself. Although this may be a bold assertion, it's a 
> hypothesis I'm considering until further clarification is obtained. 
> The configuration details for this specific VM, along with the results 
> from "fio" tests, can be found in references [3] and [4].
>
> If anyone possesses insights into how to achieve around 80,000 IOPS 
> within a fully OpenStack-operated environment, I'm eager to receive 
> such suggestions. My objective here is to bridge this gap, and I would 
> greatly appreciate any guidance in this regard.
>
> /Jan Wasilewski
>
> /References:/
> /[1] dumpxml of OpenStack managed instance with "vdb" attached: 
> https://paste.openstack.org/show/bQvGUIM3FSHIyA9JoThY//
> /[2] fio results of OpenStack managed instance with "vdb" attached: 
> https://paste.openstack.org/show/bViUpJTf7UYpsRyGCAt9//
> /[3] dumpxml of Libvirt managed instance with "vdb" attached: 
> https://paste.openstack.org/show/bGv8dT1l2QaTiAybYrJi//
> /[4] fio results of Libvirt managed instance with "vdb" attached: 
> https://paste.openstack.org/show/bOzYXkbco0oDfgaD0co8//
> /[5] xml configuration of vdb drive: 
> https://paste.openstack.org/show/bAJ9MyEWEGOteeJnH5D8//
>
> pt., 11 sie 2023 o 11:27 Jan Wasilewski <finarffin at gmail.com> napisał(a):
>
>     Hi Sven,
>
>     maybe you missed it, but kernel is provided in a link here [1]. In
>     short: 5.4.0-155-generic. If something additional is needed, just
>     let me know.
>     /Jan Wasilewski
>
>     /[1] https://paste.openstack.org/show/bcGw3Glm6U0r1kUsg8nU//
>
>     pt., 11 sie 2023 o 10:48 Sven Kieske <kieske at osism.tech> napisał(a):
>
>         as a last resort, what kernel is that ubuntu 20.04 running?
>
>         I'd advise to use the HWE Kernel at least, maybe even test latest
>         kernel.org <http://kernel.org> LTS release.
>
>         HTH
>
>         -- 
>         Sven Kieske
>         Senior Cloud Engineer
>
>         Mail: kieske at osism.tech
>         Web: https://osism.tech
>
>         OSISM GmbH
>         Teckstraße 62 / 70190 Stuttgart / Deutschland
>
>         Geschäftsführer: Christian Berendt
>         Unternehmenssitz: Stuttgart
>         Amtsgericht: Stuttgart, HRB 756139
>
>