[Openstack] guest rbd block device speed limit

Chris Friesen chris.friesen at windriver.com
Thu Aug 24 15:14:40 UTC 2017

On 08/24/2017 01:04 AM, chagg at foxmail.com wrote:
> Hello:
>      I  am using openstack + libvirt + qemu-kvm. The speed of copying files
> between virtual machines exceeds 300M Byte per second but the speed of dd command:
>   "watch dd oflag=direct,nonblock if=/dev/zero of=/opt/iotest1 bs=4M count=10"
>   is around 20M byte per second. Every guest is the same, and there is no io
> tuning in libvirt. What can I do to unleash the speed of disk io speed inside
> the guest?
>      Thanks!

It looks like you're using ceph for your root disk.  What sort of performance do 
you get accessing the ceph volumes from the host?


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