On 08/20/2015 10:39 AM, J-P Methot wrote:
Hi,
I've made a custom centos 6.7 image on a proxmox with kvm hypervisor
with the goal of using it with openstack. I setup all the necessary
cloud-init packages that are needed by openstack. Everything seems to
work fine on openstack, except that the drive speed in fio is about 50%
of what I can achieve on other images.
Basically, on a ubuntu 14.04 with the following FIO command, I can reach
about 1 GB/sec :
fio --name=testfio --filename=testfio --bs=4m --rw=write --size=5g
However, on my centos 6.7 image, I will only reach about 400 MB/sec. Why
is there such a huge discrepancy between both OS? I've always used
virtio, both on the proxmox hypervisor and on openstack.
I cannot speak to disc performance, but I can say there is a large
difference in network performance between an instance running CentOS7
with its 3.10 kernel, and an instance running either 14.04 (3.13) or
15.04 (3.19). There were virtio_net driver changes around buffer
handling which appear to be the cause. Perhaps something similar
happened for the disc I/O path and what is likely the even older kernel
in CentOS6?
happy benchmarking,
rick jones
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