Work Underway To Return Xen Support To Fedora 13

Julie188 writes "Details on this are admittedly sketchy, but both Red Hat and Xen.org have gone on record promising that some kind of support for the Xen hypervisor is forthcoming for Fedora users. As we know, on Monday, Fedora 13 was released, chock full of features to appeal to business users. One of the ballyhooed improvements to 13 is virtualization — meaning KVM and only KVM — for Red Hat. Xen was dropped from Fedora a few releases ago and it hasn't come back in 13, except that 13 still supports Xen guests. Meanwhile, 'work is underway in Xen.org to add platform support to Fedora 13 post-release,' promises Xen.org's Ian Pratt."

Comments

KVM catches Xen

[Pecisk]

As more new servers are deployed for virtualization, Xen superiority over KVM slowly, but surely disappears. First of all, all new tech has virtualization acceleration support in CPUs. Now, for example, using KVM in combination with paravirtualized network and storage drivers (which are packaged and used in Ubuntu as default), Ubuntu Server 10.04 LTS has the same speed and performance as guest as using Xen. Also huge improvements into libvirt stack and virt-manager have played role here - yes, I know, Xen also can use libvirt, but still - as it is more and more easier to deploy virtual machines, be it development or server environment. I have worked with Xen exclusively in the past for some three years, and most problems have been kernel patching issues and in fact, HVM support (because you still have to emulate some devices with quemu, which leaks like crazy, I guess that's reason why KVM now uses paravirtualized devices for net/storage). I don't have time to compile code for production servers, so if KVM is in kernel, and it is supported by kernel team and distribution, I will go for it. I was reserved And I guess lot of newcommers in virtualization will too.

In nutshell, Xen devs shoot in the foot here. Have they agreed to be included in main kernel three and be more welcome with patches, it would be more interesting competition here.

Re:KVM catches Xen

[hax0r_this]

I was responsible for maintaining a Xen environment for about a year and a half and had much the same experience. We compile our own kernels and in this regard Xen was a nightmare. Do I stick with a 2.6.18 kernel which is the latest supported? If we do that we have to make sure to get backported security fixes. Or do we use forward-ported Xen patchsets which weren't all that reliable and were a pain in the ass to apply?

We finally switched to KVM and suddenly life got a lot easier.

(Going slightly off topic here)For a while we used libvirt and the associated tools, then we discovered Ganeti, a project at Google which has made cluster management a breeze. Libvirt has a "network" driver, but really isn't designed to manage redundant virtualization clusters. Ganeti, on the other hand, is designed specifically for managing clusters, and takes care of all the dirty work like setting up and managing LVM and DRBD. You can build out a new virtual machine, complete with an operating system in just one command, or even do it over the HTTP API. You can use Ganeti with KVM or Xen, but until/unless Xen is in mainline I won't be touching it.

Xen needs to improve

[Alain Williams]

I liked the idea of Xen and tried to use it for some time, however:

• The (free) management tools were bad. If you wanted to do anything other than something quite simple, it was hard or impossible
• The documentation was hopeless: not complete; not enough examples; out of date

An exciting technology that I hoped to use, but just not up to the mark.

Where it belongs...

[Chris Snook]

Fedora, not RHEL, is really where Xen belongs anyway. It's exactly the sort of mix of neat ideas, dirty hacks, and blatant wheel re-invention that could only have come from academia, and it was only ever made enterprise-grade by throwing heaps of money at it, and even then only for carefully tested configurations. Yes, it's pretty much single-handedly responsible for commoditizing virtualization, but the combination of the design and the lack of cooperation with the kernel community made it a nightmare to support. Xen is responsible for the existence of KVM because it showed such immense promise, and then delivered extreme frustration and pain.

Since Xen decided long ago it was going to be the center of its own universe, it's really in a great position to do cool experimental things that the kernel community would be more cautious about and the enterprise market wouldn't touch with a 10' pole without seeing a strong proof of concept first. That kind of innovation is a stated goal of the Fedora project.

The only technical advantage Xen enjoys right now is a lack of dependency on hardware virtualization features. Since it's impossible to buy a new machine that you can call a server with a straight face that lacks hardware virtualization, this is meaningless in the enterprise world, but Fedora (like other community distros) has a much broader scope, so there's still a real chance there for necessity to give birth to more invention, much like it did in the early days of Xen when x86 hardware virtualization was still a whisper in the halls at Intel and AMD.

Of course, Xensource/Citrix has already driven away most of the community that would have done this kind of pre-product development, so I'm not holding my breath, but it would be nice to see something more to come of all that work (and years of my own life) beyond simply supporting existing users.

KVM is also compatible

[thule]

Plus, KVM has xenner that provides Xen compatible devices to virtual machines. I also saw some patches going into KVM that provide Hyper-V hypercalls to KVM. Right now they are fairly basic, but it is a start.

There is no doubt that KVM is the future. It is built into the kernel -- no dom0 patches required. RedHat is heavily investing in it. Note the sponsored oVirt project that integrates libvirt and FreeIPA to manage a network of virtual machine servers using kerberos and ldap as the security framework.

Re:Can someone explain the point of hypervisors?

[betterunixthanunix]

Here is a scenario for you: you have some old server that is going to be decommissioned, but it is running some important software, and perhaps a different operating system from all of your other servers. On the one hand, you can go ahead and configure a new system...or with virtualization, you can simply take a snapshot of the hard disk image and run a VM on some other server (perhaps one that is underutilized).

In general, the point of virtualization in a server room is flexibility. VMs are easy to move around, you do not have to be tied to a single operating system (I hear the most common use of KVM is to run Exchange on system with a Linux hyperviser) on a single physical machine, which is particularly useful for sharing hardware resources when you have to deal with software that only runs on a specific OS. VMs also make it easy to checkpoint a system; KVM has "copy on write" disk images, for example, which track changes from a base image, which could be a COW image itself.

IBM did a lot of research on virtualization use, and I believe they had discovered uses for using VMs within VMs up to four layers deep (I am not really sure what they were doing).