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Why KVM Whips OpenVZ's Ass for Webhosting
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Why KVM Whips OpenVZ's Ass for Webhosting

'Cause the memory you bought actually gets used (file caching):

512MB OpenVZ

Memory

Applications :    59 MB
B/C          :   103 MB
Free         :   350 MB  <---
Free (-B/C)  :   453 MB
Swapped      :    14 MB

512MB KVM

Memory

Applications :   51 MB
B/C          :  439 MB
Free         :    7 MB <---
Free (-B/C)  :  447 MB
Swapped      :    0 MB

Comments

  • AnthonySmithAnthonySmith Member, Patron Provider

    I like these posts :)

    what about for none cached, you will get higher random read latency on KVM usually.

  • AnthonySmith said: what about for none cached, you will get higher random read latency on KVM usually.

    For me, if it starts to affect load and performance I either migrate some sites to another box, upgrade RAM, or bitch at the provider, whichever seems appropriate :)

    Thanked by 1inthecloudblog
  • NekkiNekki Veteran

    Something I never actually considered.

  • On OpenVZ, file-caching is managed by the host node. The more 'crowded' the node, the less file-caching you'll achieve.

    On KVM (and Xen) file-caching is managed by your VM.

    Thanked by 1vimalware
  • Doug your posts are always great

  • Definition of OpenVZ container:
    Just an advanced chroot with memory/CPU limits

    Definition of KVM VPS:
    Full virtualization, resources are yours.

    Thanked by 1getvps
  • I love OpenVZ :) But sometimes it's not the right solution for the job at hand.

    Thanked by 1inthecloudblog
  • OpenVZ should die.

  • @FlamesRunner said:
    Definition of OpenVZ container:
    Just an advanced chroot with memory/CPU limits

    Definition of KVM VPS:
    Full virtualization, resources are yours.

    You need to re-read the dictionary.

    Thanked by 1aldothetroll
  • FlamesRunnerFlamesRunner Member
    edited July 2015

    While it is true that resources technically can be oversold (CPU and RAM) in KVM, KVM gives you the feeling of being in a dedicated server. On the other hand, OpenVZ is more or less a virtual environment, with disk caching and whatnot only enabled when you have ploop being used. Also, OpenVZ shares the host kernel, while KVM doesn't. That's why there isn't a kernel overhead when we use OpenVZ.

    Anyways, both have their advantages - OpenVZ is very efficient, without loss of any resources, and KVM, full virtualization with Windows support should you require it.

  • OpenVZ is good for me. Root access, ability to run anything on there and no overhead

  • smansman Member
    edited July 2015

    I run OVZ and KVM side by side doing the exact same thing (LAMP). I can tell you without hesitation that when comparing apples to apples OVZ greatly outperforms KVM. It's not even close. Administering it is much easier in just about every way also.

  • KVM: For the times when you just need Windows, FreeBSD or just a good kernel panic.

  • smansman Member
    edited July 2015

    This video talk by James Bottomley pretty much lays it all out there with no BS. The history, philosophy, technology, and the future. Soup to nuts.

  • sman said: I can tell you without hesitation that when comparing apples to apples OVZ greatly outperforms KVM.

    Yes, I think we've all heard that before, and I don't dispute it. Unfortunately, in the lowend world there are other factors that often work against this inherent advantage.

  • If only it was easy to run docker in openvz.

  • noamannoaman Member

    I have one question... Do you need to ask your hosting providers to enable kernel modules in KVM too like I have to do in open VZ

  • noaman said: Do you need to ask your hosting providers to enable kernel modules in KVM too like I have to do in open VZ

    No :)

  • smansman Member
    edited July 2015

    @noaman said:
    I have one question... Do you need to ask your hosting providers to enable kernel modules in KVM too like I have to do in open VZ

    The majority of customers don't care. They don't hang out on LET and try come up with reasons why KVM is better and create a new thread about it almost every day. For the minority of people that care, they can get a KVM server. That is one of the reasons we do both.

    Speaking of LET, It's VERY relevant here because $ for $ a provider can supply the same spec VPS on OVZ quite a bit cheaper than KVM. Not necessarily because they are overselling but because the performance doesn't degrade nearly as fast.

    For example, one of our KVM hosts running RAID 10 still has completely inferior I/O compared to one of our OVZ Nodes with almost identical hardware running RAID1 and with quite a few more customers on it. The performance difference on I/O is huge. Yes we have the KVM Host and guests scheduling optimized, cache is optimized. Everything is optimized.

  • NyrNyr Community Contributor, Veteran

    sman said: Not necessarily because they are overselling

    Not overselling is just dumb.

    Thanked by 2hostnoob GM2015
  • noamannoaman Member

    @sledog
    That means modeprobe fuse wont return any errors...:-)...I have two openvz servers and hosting providers really dont enable fuse easily...I don't know why they hesitate

  • noamannoaman Member
    edited July 2015

    @sman...thanx...for the detailed...info...one more thing..why a person is limited to os listed on the solusvm...why I cannot use elementary os(example) on my openvz vps

  • noaman said: elementary os(example) on my openvz vps

    I haven't tried it out with OpenVZ. But I think it's possible because elementary is basically Ubuntu. Correct ?

    If you're running KVM. No problem

  • mikhomikho Member, Host Rep

    @noaman said:
    sman...thanx...for the detailed...info...one more thing..why a person is limited to os listed on the solusvm...why I cannot use elementary os(example) on my openvz vps

    Because there is litterally a gazillion OS version and most providers only provide the most common version.
    Some providers add the requested OS if asked for and if it is possible to run it on OpenVZ.

  • smansman Member
    edited July 2015

    @noaman said:
    sman...thanx...for the detailed...info...one more thing..why a person is limited to os listed on the solusvm...why I cannot use elementary os(example) on my openvz vps

    Anything that can run a Linux kernel is possible on OVZ. Just cannot use a custom kernel.

    You can create your own if there is no template available.
    https://openvz.org/Debian_template_creation

  • Things I don't like about OVZ:

    -may be oversold easily
    -can't modify kernel to e.g. modify the swappiness
    -can't disable swap (though OVZ swap is true RAM as well)
    -some programs which require the system to have an own kernel won't work
    -everybody who can use cd may access the files on the VM easily
    -less stable

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