On 12/17/2010 4:29 PM, Erik Brakkee wrote:
Hi,
For a backup of data from a VM to a USB mounted disk I want to
circumvent the USB 1.1 limitations on the guest and instead copy the
data over to the host using scp/ssh. I have setup a network using
virtio and NAT like this:
<interface type='network'>
<mac address='52:54:00:6b:0d:36'/>
<source network='default'/>
<target dev='vnet1'/>
<model type='virtio'/>
<alias name='net1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06'
function='0x0'/>
</interface>
What does that equate to in command line options? Check libvirt logs
maybe. What version of qemu-kvm? Guest details? Host details?
When I now create a 1GB file using dd and copy it over from the guest
to the host, I am seeing a performance between 25-30 MB/s.
Is it to and from the same disk? If so, maybe you could try a tmpfs in
the guest or host so you aren't constantly seeking back and forth on the
same disk.
Also have you tried something like rsyncd instead of scp? Maybe you are
hitting some sort of encryption limitation.
My question is if this is normal because I have seen others on the
internet achieve far greater speeds.
Depends on a lot of factors. Certainly raw bandwidth wise, virtio-net is
capable of a lot more than that. With vhost-net here, I can get over
5gbps guest to host. And that's on crappy old first gen cpus (no ept/etc.).
In any case the speeds are comparable to current USB 2.0 speeds but I
intend on using USB 3.0 so would like to get a little bit more out of it.
What would I use to speed this up a bit futher?
Cheers
Erik
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