[Xen-devel] Re: Will pv-ops dom0-patched kernel be eventually merged into Linus Torvalds' mainline Linux kernel tree?

["Mr. Teo En Ming (Zhang Enming)" <space.time.universe@xxxxxxxxx>]

One of the reasons why I prefer Xen over KVM is because of networking.

I have a Gigabit network card on my Intel DQ45CB motherboard. I don't see a need to install an additional network card on my motherboard as PCI and PCIe expansion slots are limited.

In the case of Xen, the physical network interface in my host operating system (dom0) and the virtual network interfaces in my guest operating systems (domU) can be added to the same ethernet bridge on the host OS. This implies that my host and virtual machines will have IP addresses in the same subnet. Moreover, if I do not want to configure static IP addresses, my virtual machines (VMs) can obtain IP adddresses from the DHCP server on commercial routers like Linksys, D-Link, Netgear, etc, similar to the way the physical network card on the host obtaining its IP address from the same router.

But, for the case of KVM, I need to setup an internal network for my guests. This implies that my guests will use a different subnet from the host. In order for my guests to have internet connectivity, I need to create an ethernet bridge on the host OS and configure it as the default gateway/router for my guests. Then I need to setup source network address translation (SNAT) for the virtual network interfaces in my guests. The virtual network interfaces in my virtual machines cannot obtain IP addresses from my Linksys, D-Link, Netgear routers. If I want to run services like HTTP servers on my guests, I need to setup destination network address translation (DNAT) *twice*, first from my commercial router to my host OS, but my host is also a router for the internal network of my virtual machines, hence I have to port forward a second time from my host OS to my guest machines. 

Fortunately, in the case of Xen, I would only have to setup DNAT once, from the commercial router to my virtual machine.

For the purpose of my argument for Xen vs KVM networking, please refer to the following article:

Qemu (kvm) internal network setup

Link: http://blog.cynapses.org/2007/07/12/qemu-kvm-internal-network-setup/

-- 
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@xxxxxxxxx
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

On Tue, Nov 10, 2009 at 1:29 PM, Mr. Teo En Ming (Zhang Enming) <space.time.universe@xxxxxxxxx> wrote:

After reading the following articles, it doesn't sound very hopeful for Xen.

[1] Xen vs. KVM: Verdict still out on dueling hypervisors
http://searchdatacenter.techtarget.com/news/article/0,289142,sid80_gci1368664,00.html

[2] Xen vs. KVM Linux virtualization hypervisors
http://searchservervirtualization.techtarget.com/generic/0,295582,sid94_gci1371226,00.html

[3] Xen vs. KVM: The Linux Foundation’s Small-Minded View of Virtualization
http://windowsconnected.com/blogs/brad/archive/2009/04/17/xen-vs-kvm-the-linux-foundation-s-small-minded-view-of-virtualization.aspx

What are your views? I certainly hope that pvops dom0 patches would be merged into the mainline Linux kernel.

--
Mr. Teo En Ming (Zhang Enming) Dip(Mechatronics) BEng(Hons)(Mechanical Engineering)
Alma Maters:
(1) Singapore Polytechnic
(2) National University of Singapore
My Primary Blog: http://teo-en-ming-aka-zhang-enming.blogspot.com
My Secondary Blog: http://enmingteo.wordpress.com
My Youtube videos: http://www.youtube.com/user/enmingteo
Email: space.time.universe@xxxxxxxxx
Mobile Phone (Starhub Prepaid): +65-8369-2618
Street: Bedok Reservoir Road
Country: Singapore

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