From mboxrd@z Thu Jan 1 00:00:00 1970 From: Erik Brakkee Subject: Re: network performance between host and guest... Date: Sun, 19 Dec 2010 00:03:11 +0100 Message-ID: <4D0D3DAF.3080605@brakkee.org> References: <4D0BE42E.6010309@brakkee.org> <4D0BF901.5020503@theiggy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm To: Brian Jackson Return-path: Received: from cpsmtp-fia04.kpnxchange.com ([195.121.247.8]:4247 "EHLO cpsmtp-fia04.kpnxchange.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757188Ab0LRXDP (ORCPT ); Sat, 18 Dec 2010 18:03:15 -0500 In-Reply-To: <4D0BF901.5020503@theiggy.com> Sender: kvm-owner@vger.kernel.org List-ID: Brian Jackson wrote: > 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: >> >> >> >> >> >> >> >>
> function='0x0'/> >> > > > 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 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > You are right. I was indeed not so smart of me. I was assuming that the overhead of SSH would be negligible. However, I am seeing similar transfer speeds when I copy a file on the localhost to the localhost using SSH (on the host, not even on a guest). Netperf tests of the network show much higher speeds (approx 900Mbps) so the network is not the problem. The bottleneck is definitely SSH.