Best Practice - RHV IO Threads

Latest response

Is there a recommended, or best practice, when determining the number of threads vs the number disks when enabling 'IO Threads'? For example, a ratio of 1:2 (1 thread for 2 disks)?
Thank you,

DT
Log in to join the conversation

Responses

Jamie Bainbridge's picture Red Hat Guru 7257 points
3 May 2018 11:20 PM

Upstream libvirt suggests 1-2 threads per host CPU:

Note that libvirt allows a domain to specify the I/O threads that it uses. I'm not sure how RHEV handles that, if at all. You may have to write a custom hook if you want that granular level of control:

DT Active Contributor 150 points
4 May 2018 2:24 PM

I'm talking about the IO threads on the VM. If you right click a VM, select 'Edit' then go to the 'Resource Allocation' tab, there's an option to enable 'IO Threads' and a text box to set 'Num Of IO Threads'. It's my understanding enabling IO threads treats the disk as separate threads from the host perspective, instead of lumping all IO work associated to the VM to just one thread.

https://www.ovirt.org/develop/release-management/features/virt/iothreads-support/

DT Active Contributor 150 points
4 May 2018 3:43 PM

OK. I went back and looked at the XML file for some of our VMs and looks like we're talking about the same thing. The recommendation seems to be related to the CPU's more than the disks -- 1-2 threads per CPU. Thank you for the help

Close

Welcome! Check out the Getting Started with Red Hat page for quick tours and guides for common tasks.