On 11/10/2009 04:13 PM, Pasi Kärkkäinen wrote: > On Tue, Nov 10, 2009 at 05:12:50PM +0200, Pasi Kärkkäinen wrote: >> On Tue, Nov 10, 2009 at 03:49:59PM +0100, Dennis J. wrote: >>> On 11/10/2009 03:35 PM, Grant McWilliams wrote: >>>> >>>> Both Novell and Oracle having been deeply involved in Xen lately, both >>>> are developing and supporting their own products based on Xen. >>>> >>>> -- Pasi >>>> >>>> ___ >>>> >>>> >>>> >>>> I have no problem with a "better" solution than Xen because to be honest >>>> it's a pain sometimes but at this point virtually all enterprise VM >>>> deployments are either based on VMware ESX or Xen (Xenserver, >>>> VirtualIron, Amazon AWS, Oracle, Sun SVM, Redhat and Suse). This tide >>>> will change as KVM becomes more dominant in the VM space but I don't see >>>> that happening for a while. I'm also a bit skeptical as to how well a >>>> fully virtualized system (KVM) will run in comparison to a fully >>>> paravirtualized system (Xen PV). I have a system with 41 VMs on it and >>>> I'll be having 2 weeks of planned downtime in the near future. I'd like >>>> to see how these systems run under KVM. >>> >>> I've been wondering about the definition of PV in the context of KVM/Xen. >>> In the Linux on Linux case for Xen PV practically means that in the HVM >>> case I have to access block devices using /dev/hda while in the PV case I >>> can use the faster /dev/xvda. When using KVM which apparently only supports >>> HVM I can still install a guest using the virtio drivers which seem to do >>> the same as the paravirtualized devices on Xen. >>> >>> So what is the KVM+virtio case if not paravirtualization? >>> >> >> KVM+virtio means you're using paravirtualized disk/net drivers on a >> fully virtualized guest.. where Qemu emulates full PC hardware with BIOS >> and all. So only the disk/net virtio drivers bypass Qemu emulation. >> (Those are the most important and most used devices.) >> >> Xen paravirtualized guests run natively on Xen, there's no need for >> emulation since the guest kernels are aware that they're being >> virtualized.. There's no Qemu emulating PC hardware with BIOS for PV guests. >> > > Oh, and Xen also has PV-on-HVM drivers for HVM fully virtualized guests > to bypass Qemu :) Which I guess makes describing a guest as "fully virtualized" or "paravirtualized" rather pointless given that there now is just a degree of how paravirtualized a guest is depending on the drivers you use. Regards, Dennis