Hi,

Please see my comments below.

On Tue, Jun 19, 2018 at 11:51 AM, Gianluca Cecchi <gianluca.cecchi@gmail.com> wrote:

On Tue, Jun 19, 2018 at 10:45 AM, Sharon Gratch <sgratch@redhat.com> wrote:
Hi Gianluca,

You are right, in oVirt 4.2 we removed the 'Num Of IO Threads' text field from the UI because it was decided that one IO thread is the best configuration from performance aspects for most cases (according to performance testings). We wanted to keep the UI simpler to use.

So in case IO threads is enabled via Webadmin UI, only one IO thread is always created.

For REST API the configuration remains unchanged in 4.2, so you can still set the number of IO threads to be >= 1 if you want for some reason.

Regards,
Sharon

Thanks for confirmation.
So I think the manual has to be updated.
Let me know if you want me to open a documentation bug or not.

yes, please open a bug on that.

Have you any suggestion on how to set from the REST API, so that I can make some tests?

Sure, for setting IO threads number via REST API, you should run the following request:

PUT http://engine:port/ovirt-engine/api/vms/vm-id

# request body:
<vm>
<io>
<threads>2</threads>
</io>
</vm>

You can replace "2" by any other number, while 0 is for disabling the IO threads.

Have you "permission" to detail better the scenario of your test cases, landing to prefer 1 I/O thread?

I wasn't the one to perform those tests so I don't have those results for sending.

Gianluca