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[nova] local ssd disk performance

Thank you Daniel,

My colleague found the same solution in the meantime. And that helped us as well.

Kind regards,

On 8/2/19 6:50 PM, Daniel Speichert wrote:
> 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) - provided the best performance, but we could not migrate our instances (seems to be a bug).
>> 2. use cinder with lvm backend  and instance locality, we could migrate the instances, but the performance is less than half of the previous case
>> 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 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