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Re: [Xen-users] Xen Performance

To: Dustin.Henning@xxxxxxxxxxx
Subject: Re: [Xen-users] Xen Performance
From: Grant McWilliams <grantmasterflash@xxxxxxxxx>
Date: Fri, 16 Oct 2009 12:19:44 -0700
Cc: "Fajar A. Nugraha" <fajar@xxxxxxxxx>, Fasiha Ashraf <feehapk@xxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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On Fri, Oct 16, 2009 at 12:08 PM, Dustin Henning <Dustin.Henning@xxxxxxxxxxx> wrote:
       Does KVM have similar options that allow for communication directly between VMs?  I only used KVM once, with one VM, to determine fully-virtualized performance was too poor (the same as in Xen, but with less driver support).  If so, I don't know why it doesn't suffer from the same issue, and I should hope Xen could be fixed.  Regardless, I am disappointed by RedHat's decision to jump ship and go to KVM.  I think xen makes more sense, and pvops would be ideal.  The primary reason I use Xen, though, is because I use Windows and KVM doesn't have the drivers yet, so I get better performance in Xen.

Things are different in KVM and there's less isolation between "DomUs" since they're basically processes. Theoretically KVM should have much faster Guest to Guest networking then Xen but less isolation. However a PV on Xen should cream KVM in just about every other aspect. I've heard and I haven't finished my testing yet to confirm this that KVM is faster than a Xen HVM doing the same tasks if they both have PV drivers which means KVM may be better solution for virtualizing Windows. I have a contract for Virtualizing 75 Window 2K systems so I'll be doing a great deal of testing in the coming months to know for sure. The KVM method is attactive because it does things the "Linux Way" though as apposed to being very invasive like Xen. For Enterprise projects I only use Xen and use KVM for development work but I keep my mind open. Most all Enterprise solutions are either ESX or Xen based which tells you something. However, it's getting harder all the time to stick with Xen because most distributions are dropping it. I'm now using Debian Lenny kernels in my Ubuntu DomUs. It may end up being only Suse that supports Xen at some point. I think Xen is a great product but if KVM can manage to do the same thing and be easier to manage Xen will sadly go away. I've sort of given up hope that it will ever have decent Dom0 support in the kernel. By the time that happens KVM will have taken over the entire Linux VM world (which makes the conspiracy theory part of my brain buzz).

Grant McWilliams
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