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KVM vs Xen?
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KVM vs Xen?

winstonwinston Member
edited August 2012 in General

Hi guys, my first post on LET (but I've been lurking for a while). I'm not sure if this is discussion-worthy but I figured since a lot of providers hang out here I would probably get some people with hangs-on experience.

Anyway, my question is what is the difference between KVM and Xen? I've seen them mentioned as separate "systems" on here several times - I thought they were the same thing, just interchangeable terms. Is there a difference?

Thanks :)!

Comments

  • with KVM you can install your own ISO, Xen you can't (persay).

  • KVM provides "more" virtualization than XEN, e.g. you can also install Windows on it. I don't think XEN has any big advantages over KVM os it will probably die out.

  • You can install windows on XEN aswell.

    KVM just allows you to control your own kernel builds and is generally more speedy than XEN

    Phil

    Thanked by 1Jeffrey
  • Xen is hard memory allocation, where KVM is soft.

  • winstonwinston Member
    edited August 2012

    I have a 512MB XEN at VPS6 right now and noticed that a MySQL server allocates a TON of RAM on OpenVZ but not Xen - would it act the same under KVM as it does XEN?

    @MrLawoodle do you mean KVM memory allocation is like OpenVZ's?

    Oh and is it allowed to create a rant discussion about a host here?

  • @winston said: @MrLawoodle do you mean KVM memory allocation is like OpenVZ's?

    Yes, soft. There is probably a better word for it though, "dynamic"?

    @winston said: Oh and is it allowed to create a rant discussion about a host here?

    If justifiable and with proof then yes.

  • does anyone notice that xen tend to be cheaper than kvm? or is it just me? thanks

  • rds100rds100 Member
    edited August 2012

    From a provider's point of view the cost for providing Xen and providing KVM (with the same resources) is almost the same. KVM probably has some more overhead, CPU wise, but not too much.
    If there is a price difference it is mostly marketing.

  • AlexBarakovAlexBarakov Patron Provider, Veteran

    KVM allows easy RAM overcommiting, where it is a bit harder for Xen.

  • prometeusprometeus Member, Host Rep

    VMWare allow ram overcommitment since the beginning (it was also a selling point in the enterprise) but this never has been a hostacle about is adoption :)

    both xen and kvm are good platform :)

  • always new tech you should choice

  • Kvm is as close to a dedicated server as you can get

  • MaouniqueMaounique Host Rep, Veteran

    KVM is the hype now because redhat withdrew xen support and went for KVM.
    BOTH Xen and KVM can install Windows, BOTH can overcommit memory.
    Xen was a variant called Xen-PV which is faster and better suited for big scale virtualization than KVM but it cannot install windows as needs the kernel to cooperate with the host, deferring IO operations to the host kernel, as such, needs a modified kernel and uncle bill will not go for that (at least not yet).
    You can do the same things with XEN-HVM as you can do with KVM, I dont think KVM is faster, tho it benefits from virtio drivers which somehow reintroduce the Xen-PV concept at another layer.
    It is ultimately a thing of fashion and war of the big linux ppl, redhat vs debian. So far redhat is winning, but I dont think Xen had the last word. Not by far.
    M

  • I definitely prefer Ubuntu - does that mean I should stick to Xen for Ubuntu?

  • MaouniqueMaounique Host Rep, Veteran

    No, you can run Ubuntu in any virtualization software.
    Proxmox is based on Debian and runs KVM like a pro, it is only Redhat that doesnt support Xen anymore.
    I prefer Xen, gives better choice IMO.
    But nothing against KVM, works too.
    M

  • Only bad thing about KVM was IO, but now we have VirtIO which fixed that nicely.

  • MaouniqueMaounique Host Rep, Veteran

    VirtIO fixed that by rethinking the Xen-PV concept. I admit it is a more elegant approach that modifing the kernel, Xen is on something similar.
    M

  • vps6netvps6net Member
    edited August 2012

    I haven't found either one to be inherently "better." As a service provider, I would prefer Xen for its versatility -- Xen PV runs very speedy Linux environments, while Xen HVM can do all the same things KVM can (that is, isolate kernels like Windows, Solaris, or anything else you might want). In my personal experience, neither Xen HVM nor KVM will benchmark significantly higher when proper PV drivers are setup, while a default Xen PV configuration usually beats them both.

    Thanked by 1Maounique
  • MaouniqueMaounique Host Rep, Veteran

    @vps6net said: I haven't found either one to be inherently "better." As a service provider, I would prefer Xen for its versatility -- Xen PV runs very speedy Linux environments, while Xen HVM can do all the same things KVM can (that is, isolate kernels like Windows, Solaris, or anything else you might want). In my personal experience, neither Xen HVM nor KVM will benchmark significantly higher when proper PV drivers are setup, while a default Xen PV configuration usually beats them both.

    Exactly my experience too !
    M

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