<div dir="ltr"><div><div>The only time we saw major performance issues with ephemeral (we're using SSDs in RAID 0) was when we ran fio against a sparse file. It sounds like you ran it against a properly filled file though, and it looks like you're on a single spinning drive, based on the fio numbers. Can you confirm? Also, what version of qemu are you running, and can you check if you have iothread enabled? "qemu-system-x86_64 -device virtio-blk-device,help" should show iothread somewhere. One other thing I can think of, did you specify directIO in your fio run?<br><br></div>I notice you have the balloon driver on. Have you had used it in a production environment that neared full? Curious what the feedback is here. <br><br></div>Warren<br></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature">Warren</div></div>
<br><div class="gmail_quote">On Wed, Jul 8, 2015 at 6:58 AM, Gleb Stepanov <span dir="ltr"><<a href="mailto:gstepanov@mirantis.com" target="_blank">gstepanov@mirantis.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hello, all.<br>
<br>
We have measured disk I/O performance on openstack virtual machines<br>
with aid of<br>
FIO tool. We've tested performance on root dist drive device, test<br>
consists of write operationby 4kb<br>
blocks to file with size 90Gb (prefilled in advance).<br>
We use qcow2 image for vm, ephemeral drive and virtio driver.<br>
All configuration goes in attachment.<br>
<br>
There are some results:<br>
<br>
test 1<br>
<br>
threads 1, 5, 10, 15, 20, 40<br>
iops 72,58,49,60,94,72<br>
<br>
test 2<br>
threads 1, 5, 10, 15, 20, 40<br>
iops 71,60,54,88,52,52<br>
<br>
test 3<br>
threads 1, 5, 10, 15, 20, 40<br>
iops 71,49,58,51,128,130<br>
<br>
test 4<br>
threads 1, 5, 10, 15, 20, 40<br>
iops 65,49,60,56,52,63<br>
<br>
As it is shown performance degraded during increasing amount of<br>
threads, also deviation of results on 40 threads is very big.<br>
Have you any ideas how to explain performance behaviour?<br>
<br>
Kind regards, Gleb Stepanov.<br>
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<br></blockquote></div><br></div>