[ovirt-users] Re: Hosted Engine I/O scheduler

Inline: On Mar 20, 2019, at 4:25 AM, Roy Golan <rgolan(a)redhat.com&gt; wrote: On Mon, 18 Mar 2019 at 22:14, Darrell Budic <budic(a)onholyground.com&gt; wrote: > I agree, been checking some of my more disk intensive VMs this morning, > switching them to noop definitely improved responsiveness. All the virtio > ones I’ve found were using deadline (with RHEL/Centos guests), but some of > the virt-scsi were using deadline and some were noop, so I’m not sure of a > definitive answer on that level yet. > > For the hosts, it depends on what your backend is running. With a > separate storage server on my main cluster, it doesn’t matter what the > hosts set for me. You mentioned you run hyper converged, so I’d say it > depends on what your disks are. If you’re using SSDs, go none/noop as they > don’t benefit from the queuing. If they are HDDs, I’d test cfq or deadline > and see which gave better latency and throughput to your vms. I’d guess > you’ll find deadline to offer better performance, but cfq to share better > amongst multiple VMs. Unless you use ZFS underneath, then go noop and let > ZFS take care of it. > > On Mar 18, 2019, at 2:05 PM, Strahil <hunter86_bg(a)yahoo.com&gt; wrote: > > Hi Darrel, > > Still, based on my experience we shouldn't queue our I/O in the VM, just > to do the same in the Host. > > I'm still considering if I should keep deadline in my hosts or to switch > to 'cfq'. > After all, I'm using Hyper-converged oVirt and this needs testing. > What I/O scheduler are you using on the host? > > Our internal scale team is testing now 'throughput-performance' tuned profile and it gives promising results, I suggest you try it as well. We will go over the results of a comparison against the virtual-guest profile , if there will be evidence for improvements we will set it as the default (if it won't degrade small,medium scale envs). I don’t think that will make a difference in this case. Both virtual-host and virtual-guest include the throughput-performance profile, just with “better” virtual memory tunings for guest and hosts. None of those 3 modify the disk queue schedulers, by default, at least not on my Centos 7.6 systems. Re my testing, I have virtual-host on my hosts and virtual-guest on my guests already.

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