On Sat, Feb 21, 2015 at 06:59:23PM +0000, Greg Langford wrote:
> I am running CentOS 6.6 x86_64 as a KVM host and have a number of
> guests running.
> 
> After some experimenting I have noticed something curious, FreeBSD
> disk performance seems to be just over half of that of a Linux guest
> with an identical configuration.
> 
> From my understanding virtio is included in FreeBSD 10.0 onwards.
> 
> My CentOS guest has approx 130MB/s when using dd to read /dev/zero and
> write it to a file on the guest file system. This is about the same
> when doing the same on the hypervisor it's self. The stats are gained
> using iotop on the hypervisor while the test is performed.
> 
> However the FreeBSD guest gets about 70MB/s maximum when performing
> the same test and is running FreeBSD 10.1
> 
> Has anyone seen this before, is it a known issue or expected
> behaviour? I have been scratching my head about it for a number of
> days now.

Please post the dd command-line and the QEMU command-lines for launching
the Linux and FreeBSD guests.

Stefan

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