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Having used RDP before, I'm not exactly thrilled with the performance I am seeing from VNC to my KVM virtual machines. The KVM host is Ubuntu 12.04 server x64. I've read that Spice is faster, and so after considerable bumbling around, I got it to work via both virt-manager (e.g. virt-viewer) and a standalone spice client.

I don't have any hard and fast figures to quote here, but the VNC remoting seems 2x to 4x faster than spice! For example, in VNC I can easily watch a Flash video, but in Spice it is very choppy. In general Unity runs ok over VNC, but is laggy over Spice.

Is this possible? Is something misconfigured?

In both cases, I am connecting to the virtual host manager from a laptop (running Ubuntu 12.10) on the LAN to view an Ubuntu 12.04 Desktop guest VM on the host. The VNC configuration on the guest used the vga display type and the spice configuration used the qxl display type. I didn't muck with the default amount of video RAM in either case.

  • with no actual configuration details, how do you expect any input on this one? Spice is faster than VNC when properly configured, moreover, it is designed to show those flash videos, while VNC is not – dyasny Mar 28 '13 at 7:52
  • I've added that the host and client laptop are Ubuntu versions 12.04 and 12.10 respectively. What additional details are needed? – hdave Mar 28 '13 at 13:03
  • the actual configurations of course - domxml for the VM, how the X server is set up in the VM, whether it uses QXL or not, whether you have the spice agent installed and running... – dyasny Mar 28 '13 at 14:39
  • Do you have QXL drivers installed in your guest? – czerny Apr 29 '15 at 16:02
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Ubuntu 12.04 is end of life, of course, but I do want to note that SPICE/QXL of that era was very early code, and on Ubuntu 12.04 in particular wasn't well integrated yet. They were still finding and fixing SPICE/QXL bugs causing slowness well past 2013. These days I don't think this question really applies anymore; SPICE is far faster than VNC for any version out in the last few years.

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