I am using the cinder-lvm backend right now and performance is quite good. My situation is similar without the migration parts. Prior to this arrangement I was using iscsi to mount a disk in /var/lib/nova/instances and that also worked quite well. If you don't mind me asking, what kind of i/o performance are you looking for? On Fri, Aug 2, 2019 at 12:25 PM Budai Laszlo <laszlo.budai@gmail.com> wrote:
Thank you Daniel,
My colleague found the same solution in the meantime. And that helped us as well.
Kind regards, Laszlo
For the case of simply using local disk mounted for /var/lib/nova and raw disk image type, you could try adding to nova.conf:
preallocate_images = space
This implicitly changes the I/O method in libvirt from "threads" to "native", which in my case improved performance a lot (10 times) and generally is the best performance I could get.
Best Regards Daniel
On 8/2/2019 10:53, Budai Laszlo wrote:
Hello all,
we have a problem with the performance of the disk IO in a KVM instance. We are trying to provision VMs with high performance SSDs. we have investigated different possibilities with different results ...
1. configure Nova to use local LVM storage (images_types = lvm) -
2. use cinder with lvm backend and instance locality, we could migrate
3. mount the ssd on /var/lib/nova/instances and use the images_type = raw in nova. We could migrate, but the write performance dropped to ~20% of
On 8/2/19 6:50 PM, Daniel Speichert wrote: provided the best performance, but we could not migrate our instances (seems to be a bug). the instances, but the performance is less than half of the previous case the images_types = lvm performance and read performance is ~65% of the lvm case.
do you have any idea to improve the performance for any of the cases 2
or 3 which allows migration.
Kind regards, Laszlo