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Thread: OpenVZ or XEN

  1. #1
    Join Date
    Mar 2009
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    OpenVZ or XEN

    Hi,

    Im planning to have a VPS but I dont know what to choose from the two. Is XEN's performance better than OpenVZ because Plans using XEN are more expensive than OpenVZ. I would be thankful if someone can enlighten me about the two virtualizations.

    Thanks

  2. #2
    Join Date
    Sep 2005
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    London
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    XEN is a *real* virtual private server. In most cases with guaranteed ram/storage and even CPU. As a provider you can oversell using XEN, but its harder. Typically XEN's run on their own individual kernel.

    OpenVZ is a *container* - so an attempt to contain a part of a physical servers resources and dedicated them to a server-kinda-thing. Typically containers (either virtuozzo or openvz) has what providers like to call burstable resources, which means that one container can eat into the available resources of another container. You may get a guaranteed amount of resources, but quite often an OpenVZ is sold on the max rather than the real resources available. In that way a OpenVZ based VPS is much like traditional shared hosting and general overselling is very common. OpenVZ containers share the kernel with the other containers on the same physical server.

    The lack of overselling plus the overhead of running its own kernel typically ends up making XEN the more costly one.


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  3. #3
    Join Date
    Apr 2009
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    Here's an answer I prepared earlier

    Xen -> greater isolation, more overheads=lower performance
    OpenVZ -> better 'bang for buck'

    You can think of it like this:

    In OpenVZ you have a house:
    - Each VPS rents a room
    - Shared resources: bathroom, kitchen, lounge etc (which could be large = 'burst')
    - Greater spread of cost
    - Potential problems ('i hate my flat mates!')

    In Xen you have a apartment block
    - Each node has an apartment
    - Each node has their own bathroom, kitchen etc
    - More duplication, more overheads, more cost

    There is no 'best' approach, it's preference and requirements :-) One of the reasons for the cost difference is that overcommitting (not necessarily overselling) is a generally accepted solution with OpenVZ providers, or rather I should say, it's not a common practice with Xen providers, which allows for lower price points.
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  4. #4
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    That's a great analogy.
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  5. #5
    The isolation provided by Xen is better + allows for a bit more configuration at the kernel level.

    HOWEVER

    With the additional overhead of Xen, and everyone knows higher overhead means less performance, factoring into the equation that Xen is usually more expensive from a price vs resource standpoint, I prefer OpenVZ.

    I however do agree that using OpenVZ's "burst" memory does make it much more like a shared hosting environment. I fully think that if you're selling virtual private servers, that users resources should be dedicated specifically to them selves. I personally frown upon providers using "burst" and then choose to market their VPS as being isolated and that their resources being guaranteed, however that is simply my personal opinion. Some people will have the argument of something like, "well if the resources are there but not being used right that second, then why shouldn't someone be aloud to use them?" Well then I just say eh :-/

  6. #6
    Can SLM memory be oversold? It seems like most of the reputable providers are using it now. It was my understanding that SLM is true, dedicated memory for your VE and your VE alone.

  7. #7
    Join Date
    Aug 2000
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    2,754
    I personally prefer Xen

    I've used many OpenVZ providers and a number of Xen Providers - I find Xen nodes to have less issues because of it being harder to oversell the resources, i've had more problems with run away scripts on OpenVZ providers than I care to remember.

  8. #8
    Join Date
    Sep 2003
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    33
    Quote Originally Posted by missilemike View Post
    Can SLM memory be oversold? It seems like most of the reputable providers are using it now. It was my understanding that SLM is true, dedicated memory for your VE and your VE alone.
    SLM can use swap space (not in the VPS but on the host node), so it does still allow overselling of the RAM.

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