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  1. #1

    KVM or OpenVZ, for a VPS?

    I am a beginner and I am thinking to buy a VPS for myself. I see many providers offering OpenVZ and KVM, but I am not sure which one to go with.

    I read up few articles, from what I understand KVM provides full isolation and kernel is not shared. And also Open Vz is seems cheaper for the same config of KVM.

    But I only care about performance. So does isolation play any role in performance?

    When I am getting 256MB of VPS with KVM, how much of that memory will be usable for my applications? (since kernel is not shared, it will also take up memory in this 256MB?) and in the same way, do I get full 256MB usage for my applications in OpenVZ since Kernel is shared?

  2. #2
    Join Date
    Dec 2011
    Tulsa, OK
    You are correct KVM is isolated/full virtualization and OpenVZ is container based and can be oversold. What is the VPS going to be used for (e.g. web hosting, email, DNS, VPN, etc.)?

    You pretty much have an understanding of the key differences.

    I would also point out if you need a windows VPS it will not work with OpenVZ (Linux only) you would have to go with KVM in this case.

    Performance wise some say KVM is slower and OVZ is's debatable. IMO, It really depends on the provider's configuration of the KVM host node.

    You can reference these threads:

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  3. #3
    that depends.

    if you use more cpu, than KVM is best option (you get what you pay)

    KVM => Virtual dedicated server (VDS)

    openVZ => kernal is shared, i think , but easy to maintain => click reinstall and all in one click
    Simple and awesome

  4. #4
    Join Date
    Dec 2007
    My choice will depend on VPS memory.
    Less than 512 MB -> OpenVZ
    512 MB or more -> KVM

    Remember, openVZ may perform better in most cases. But OpenVZ node is generally oversold.
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  5. #5
    Join Date
    Jun 2011
    It depend on what provider you choose, it would better choose openvz in good prvider than kvm on the bad one

  6. #6
    Join Date
    Feb 2007
    USA, UK, Singapore
    KVM is full virtualization and provides 100% isolation with kernel running inside your VM. Also, as mentioned above, it is not possible to oversell KVM VM's while it is possible for OpenVZ (and that's the reason why OpenVZ's are cheaper)..
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  7. #7
    Thank you all for replying guys.

    I have decided to go with Ramnode. I checked out reviews and they are fine. So seems a reliable provider.

    In there plan, they have KVM vs Ovz and SSD vs SSD-cached... I am thinking to go with Ovz and SSD cached (I hope SSD cached is not very slow). Following is the config for 7USD/month (before applying any discount coupons):

    512MB CVZ-E5
    Starting from
    $7.50 USD
    512MB RAM
    512MB VSwap
    2 CPU Cores @ 2.3GHz+
    120GB SSD-Cached HDD Space
    1Gbps Port
    2000GB Bandwidth
    1 IPv4 Address
    16 IPv6 Addresses
    Monthly Remote Backups

    But the monthly 6USD, KVM SSD Cached plan is like this :
    256MB RAM
    1 CPU Cores @ 2.3GHz+
    20GB SSD-Cached HDD Space
    1Gbps Port
    1000GB Bandwidth
    1 IPv4 Address
    16 IPv6 Addresses
    Monthly Remote Backups

  8. #8
    Thanks and enjoy!
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  9. #9
    Well both KVM and OpenVZ can be oversold. but at this config 256MB I would suggest to go with OpenVZ
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  10. #10
    Join Date
    Nov 2005
    Michigan, USA
    All of the VPS technologies can be overcommitted (or oversold) now, but even before that it was possible for a host to easily oversell.

    An easy example: A host using the OLD version of Xen couldn't overcommit memory or disk space, but had no issue with CPU or disk I/O. So let's look at how easily these can be oversold with any technology:


    A Dual Processor system with 512GB of RAM: 500 1GB servers, massively overcommitting the CPU but has never been restricted on any VPS technology.

    Disk I/O
    The same server with 8x4TB Hard Drives: 500 servers trying to use 8 SATA hard drives would be a disaster in terms of random I/O (IOPS) even though they may be able to push 800MBPS in sustained speed and have ~30TB of usable storage.

    The moral of my story is choose based on the provider, not on the technology. This is a simple guide, unless you need Windows/Unix or a custom kernel, the technology really doesn't make a difference. If a host is clearly selling KVM for way more expensive than OpenVZ, then they are not utilizing either properly. OpenVZ, by its nature, would be more efficient and therefore cheaper, but not significantly cheaper.
    Attached Thumbnails Attached Thumbnails WhichVPS.png  

  11. #11
    For low RAM like 256MB I would prefer OpenVZ. An OpenVZ container can start with just 15-20MB of RAM, that's not possible with KVM because of the better isolation.

  12. #12
    Join Date
    Nov 2012
    KVM is true virtualization where the VPS operates as its own server, independently of the host node. OpenVZ is a container style of virtualization which relies on the host node's kernel. KVM has no restrictions in terms of functionality, but it has more overhead than OpenVZ. OpenVZ is constrained by the host node kernel, but it has less overhead in the containers themselves.

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  13. #13
    Why not have a try with DigitalOcean?They offer 512M KVM with full SSD disk for $5/mo. And the performance is great.

  14. #14
    Join Date
    Dec 2013
    KVM CAN BE oversold! You cant limit i/o or CPU...
    Even though if you dont need to use "custom" kernels IMO there is no reason to get a KVM

  15. #15
    Join Date
    Mar 2013
    Quote Originally Posted by MWN Benji View Post
    KVM CAN BE oversold! You cant limit i/o or CPU...
    Even though if you dont need to use "custom" kernels IMO there is no reason to get a KVM
    If I am correct you can oversell memory as well.

  16. #16
    Join Date
    Dec 2013
    Quote Originally Posted by slyjackal View Post
    If I am correct you can oversell memory as well.

    On KVM only Disk Space cant be overcommited

  17. #17
    Go with OPenVZ , but Don't go for Providers selling servers for 2-4$/months.

    Go with Standard Ones,

  18. #18
    ^already bought one from Ramnode

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