Re: [Xen-users] Xen vs VirtualBox

["Grant McWilliams" <grantmasterflash@xxxxxxxxx>]

On Mon, Sep 15, 2008 at 8:53 AM, Emre Erenoglu <erenoglu@xxxxxxxxx> wrote:

Hi,

On Mon, Sep 15, 2008 at 4:56 PM, Grant McWilliams <grantmasterflash@xxxxxxxxx> wrote:

Don't get me wrong, I do believe Xen is a great project and I only use it and VirtualBox for contracts but integration is key. KVM will be in every Linux distribution on the planet and at some point it will do what Xen does. My biggest problem with it (outside of the fact that it feels like I'm just using a faster QEMU) is that it requires VT support in the CPU. There are many older really fast machines with tons of ram that you just can't use KVM on. VirtualBox, VMWare and Xen run on just about anything.

Well i'm just an enthusiast in these virtualization stuff. I played with Xen since its 2.0 days. After all the issues I had with it, lacking kernel stuff, unstability in distribution dom0 kernels etc, I left it for the moment for KVM.

yes KVM needs VT support  but that's becoming commodity now. Nevrtheless, you're right for the older machines.

For performance, it's getting better and better, with virtio stuff embedded in all kernels, my guests can make gigabits/sec transfers on network connections. With very little work.

the management infrastructure like libvirt will more and more support KVM, so it will only go better.

Emre

Can people start "replying to all" instead of sending me personal messages? It's much more productive for the list.

Xen is a very different animal now and is very good and rock solid. Because it's integrated into the two largest Linux server distros it's very easy to set up an use as long as you understand the concept of what Xen does. Interestingly the reasons you left Xen for KVM are exactly the reason that I won't use KVM in production. The last stable version in the RHEL line is about 36 versions old and I've had issues with that locking up. KVM is in my future but for now I just watch it and hang out on the dev list to keep an eye on their progress. Yes there are commodity motherboards with VT support but we're not using that level of equipment on big projects. I have 3 racks with dual 2.8 ghz dual-core Xeons and 8 GB of ram each that can't run KVM. Commercial Xen is probably the fastest thing out there short of ESX server which may have an edge. In certain areas KVM is getting there like network and disk access using the PV drivers. But again nobody's going to use beta PV drivers in a production environmnet. KVM needs to bake longer. Xen and ESX have both been out there longer and are very stable.

Libvert at this point is just not powerful enough. I still use the Xen config files and xm. I look forward to the time where we can have one interface to all VM products though.

I would like to see QEMU moved to being a central repostitory though because all of them (Xen, KVM, and VirtualBox) rely heavily on QEMU and make modifications but the QEMU in each is not the same version. They contribute upstream but it seems to take forever for something from VBox to get to KVM or KVM to Xen. KVM IS QEMU with an accelerator according to the QEMU people. The KVM guys don't like thinking of it that way though and I think VBox relies heavily on QEMU although VBox is much more powerful. Xen only uses it in HVM mode. I think the QEMU in Xen is the oldest which explains why KVM is faster than Xen  HVM (but can't compete in pure PV mode).

--
Grant McWilliams

Some people, when confronted with a problem, think "I know, I'll use Windows."
Now they have two problems.

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