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  1. #26
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    Quote Originally Posted by InsDel View Post
    So if I run 'ps aux' on my box, the 'guaranteed' measurement corresponds to RSS, while the 'burst' measurement corresponds to VSZ?
    Not necessarily. Memory accounting on Linux is actually quite a complex matter. OpenVZ's user bean counters tried to simplify it for each VE, but at the end it is not really doing an optimal job...

    VSZ is the virtual memory size of your process -- that includes the memory that has been allocated, process/thread stack, shared library etc. It's closely related to privvmpages (allocated pages) but the readings from `ps aux` is not that accurate due to shared libraries.

    RSS is the residential memory, i.e. the actual physical memory used by this process. It should be corresponding to the held amount in oomguarpages in a non-overselling/non-swapping scenario. I think if your process gets swapped out on the physical server, RSS will reduce, but oomguarpages will actually stay the same (which is when your physpages is different from oomguarpages).

    And although beancounters are tracking two metrics (privvmpages/guaranteed and oomguarpages/burstable), I think there is really pointless to track the GUARANTEED memory due to the ability to swap on the host node. The "guaranteed" amount there is only to guarantee that your processes will not be killed during an OOM event. It can go above the barrier amount as long as the server does not run out of memory (OOM). HOWEVER, in order to reach an OOM event on a Linux server, you usually have to exhaust all the physical memory AND all the swap -- which by then the whole server will be extremely slow anyway and your processes are about as good as dead...

    Therefore -- just worry about the burstable memory Remember that's the amount your processes "allocated" rather than "used". So for programs doing slab allocation can usually kill the whole system as they allocate a lot more than they use (i.e. Java). Multi-threaded apps also use a lot more memory on OpenVZ as each thread has default 8MB stack on Linux, which again is allocated but rarely used.

    Yeah. Pick Xen or KVM if you can.

  2. #27
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    Everyone is choosing Xen Is there anyone out there who wants to use OpenVZ?
    Learning...

  3. #28
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    Xen

  4. #29
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    Xeeeeeeeeen!!!

    Although OpenVZ could be alright for a temp VPS (for testing or something) as it's cheap.

  5. #30
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    It depends how you intend to you the VPS both system has their own advantages and disadvantages, but i assuming i can only keep one for my own use i'll prefer Xen VPS.
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  6. #31
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    Xen for me

  7. #32
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    +1 for xen
    - do it your self.

  8. #33
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    Seems most admins here want XEN, why openvz are the majority is WHT VPS offers?

  9. #34
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    Cool

    Quote Originally Posted by NelsonT View Post
    Seems most admins here want XEN, why openvz are the majority is WHT VPS offers?
    Because it is cheaper and easier to oversell I guess :8
    Learning...

  10. #35
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    Quote Originally Posted by jamjam View Post
    Because it is cheaper and easier to oversell I guess :8
    Cheaper how? They're both free. Easier to oversell, definitely, but then overselling isn't necessarily a problem in itself. Overloading and mismanagement will cause problems on any platform.

    OpenVZ is more like shared hosting in its resource allocations so it can give hosts more profit and give users more bang-per-buck. Check the benchmarks thread if you don't believe this. The major downside (as with shared hosting) is the risk of another user taking too much of the shared resource pool and affecting other VPSs. The solution (as with shared hosting) is good management / monitoring by the provider.

    Another quite separate issue with OpenVZ is the arcane UBC memory management that hardly any users seem to understand, so they may end up getting less than they expect. Then again, if they're expecting something equivalent to a dedicated server for $5 per month they're going to be disappointed anyway...

    Shared hosting - OpenVZ - Xen/KVM etc. all have their place. Users can choose whatever suits their needs.
    Chris

    "Some problems are so complex that you have to be highly intelligent and well informed just to be undecided about them." - Laurence J. Peter

  11. #36
    Greetings:

    Xen and VMWare over OpenVZ; all three are free.

    Thank you.
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  12. #37
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    Free VMware version is not for selling, is it?

    Quote Originally Posted by dynamicnet View Post
    Xen and VMWare over OpenVZ; all three are free.

  13. #38
    Greetings:

    It all comes down to packaging.

    Thank you.
    ---
    Peter M. Abraham
    LinkedIn Profile

  14. #39
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    Virtuozzo has alot less overheads compared to XEN.
    IMHO, for most applications, Virtuozzo would deliver better performance.

    How many clients want to install their own kernel or configure a SWAP?
    Cost-Benefit Analysis...
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  15. #40
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    Quote Originally Posted by dynamicnet View Post
    Greetings:

    It all comes down to packaging.

    Thank you.
    Perhaps some details?

  16. #41
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    Quote Originally Posted by Yash-JH View Post
    Virtuozzo has alot less overheads compared to XEN.
    IMHO, for most applications, Virtuozzo would deliver better performance.

    How many clients want to install their own kernel or configure a SWAP?
    Cost-Benefit Analysis...
    True, it really depends on what the client intends to run. I guess I just have a bias toward a platform that feels more like running physical hardware. From a cost standpoint VZ is more cost effective.

  17. #42
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    Quote Originally Posted by MikeTrike View Post
    True, it really depends on what the client intends to run. I guess I just have a bias toward a platform that feels more like running physical hardware. From a cost standpoint VZ is more cost effective.
    Well if the client is simply looking at installing applications, openVZ would also deliver better performance (lesser overhead).
    For the same number of nodes per server, OpenVZ may perform better.

    The additional virtualization overhead that comes with XEN, may only be desired of the client truly wishes to deal with the operating system layer - such as the kernel.
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  18. #43
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    Quote Originally Posted by Yash-JH View Post
    Well if the client is simply looking at installing applications, openVZ would also deliver better performance (lesser overhead).
    For the same number of nodes per server, OpenVZ may perform better.

    The additional virtualization overhead that comes with XEN, may only be desired of the client truly wishes to deal with the operating system layer - such as the kernel.
    That's exactly what I was hinting at.

  19. #44
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    I prefer xen, because I find it less restricted in what you can and can't do.
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  20. #45
    Quote Originally Posted by Yash-JH View Post
    Virtuozzo has alot less overheads compared to XEN.
    IMHO, for most applications, Virtuozzo would deliver better performance.
    even if this were true, a customer is still reliant on their upstream to not oversell the hell out of the server and leave them competing for resources..

    How many clients want to install their own kernel or configure a SWAP?
    Cost-Benefit Analysis...
    Isnt this what managed services are supposed to cover? I know if we asked our clients to install their own kernel or configure swap, they would likely look at us pretty funny - doesnt mean you can just neglect the benefits of real virtualization and attempt to claim that somehow there is an advantage to software level virtualization because a customer doesnt need to install their own kernel.. sure, its easier for the provider to manage this way - but, I am not so sure its better for the clients - I guess it depends on what customers are after.. but, to use your cost-benefit analysis - it would not be overly difficult to present an alternate analysis here..

  21. #46
    Quote Originally Posted by foobic View Post

    Shared hosting - OpenVZ - Xen/KVM etc. all have their place. Users can choose whatever suits their needs.
    exactly - and very well said...

    worth noting - Xen essentials offers some advantages you are not going to get from something like OpenVZ and Viruozzo - but, aside from that, I completely agree with your comments.. very well said..

  22. #47
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    Quote Originally Posted by cartika-andrew View Post
    even if this were true, a customer is still reliant on their upstream to not oversell the hell out of the server and leave them competing for resources..
    Of course. Carefully choosing your provider is important.

    Isnt this what managed services are supposed to cover? I know if we asked our clients to install their own kernel or configure swap, they would likely look at us pretty funny .
    But don't you agree, it's a burden to deal with Kernel upgrades and swap issues for the clients that simply are looking to install custom applications/services?
    Yes, there may be providers out there that slap a premium to do this for them, but why deal with that when the Virtualization platform can take care of that for you?
    IMHO - I feel there is a virtualization market out there for customers that wish to have the kernel layer abstracted from them, yet want the full advantages of a dedicated server (custom applications, etc)

    doesnt mean you can just neglect the benefits of real virtualization and attempt to claim that somehow there is an advantage to software level virtualization because a customer doesnt need to install their own kernel.. sure, its easier for the provider to manage this way - but, I am not so sure its better for the clients - I guess it depends on what customers are after.. but, to use your cost-benefit analysis - it would not be overly difficult to present an alternate analysis here.
    Real Virtualization?
    IMHO, XEN adds alot of overhead with their HyperVisor layer. My experience comes from the Windows side of the market, and Microsoft has been pushing for granularity in their operating system. This means, the operating system itself would be able to set limits on processor utilization and memory space
    Why use a HyperVisor for that?

    It is debate-able, even in the Linux front, that XEN's HyperV can do a better job at process, IO and memory scheduling then the Linux kernel. In one study I read, cache misses were far more common on XEN, compared to a Linux Kernel - suggesting that XEN may not be doing the most efficient job in process scheduling. I'd argue the same would apply to memory and disk I/O. Let us think of it this way - the Windows or Linux kernel has direct access to the system's process queue, and can choose the best way to schedule usage of the CPU or the disk. With a HyperVisor such as XEN in between, alot of this is hidden from it, and it has to decide what Operating System rather than process to schedule first (please correct me if I am wrong).

    Hence, XEN will always represent an overhead compared to OS-level virtualization. Yes, there are advantages to this - it provides complete OS-level isolation. BUT, I would argue, with Operating System design becoming more granular, these sand-boxes could also be created on the system itself, without the overheads of a 3rd party HyperVisor. This is the philosophy of OpenVZ or Virtuozzo. And it too, IMO, is Real Virtualization.
    Last edited by Yash-JH; 12-22-2009 at 02:18 AM.
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  23. #48
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    Quote Originally Posted by Yash-JH View Post
    Of course. Carefully choosing your provider is important.



    But don't you agree, it's a burden to deal with Kernel upgrades and swap issues for the clients that simply are looking to install custom applications/services?
    Yes, there may be providers out there that slap a premium to do this for them, but why deal with that when the Virtualization platform can take care of that for you?
    IMHO - I feel there is a virtualization market out there for customers that wish to have the kernel layer abstracted from them, yet want the full advantages of a dedicated server (custom applications, etc)
    A proper managed environment includes the kernel. One size fits all does not exist with managed dedicated servers, the same applies here. If a customer is purchasing a managed VPS from a reputable company, the company can afford to not be lazy, and manage the kernel level as well. Minor kernel tweaks can drastically improve performance among other things, not to mention more flexibility when it comes to running a more recent kernel. Most quality managed providers include this support in their base management packages. It is not a premium feature by any means in the quality managed hosting arena.


    Quote Originally Posted by Yash-JH View Post
    Real Virtualization?
    IMHO, XEN adds alot of overhead with their HyperVisor layer. My experience comes from the Windows side of the market, and Microsoft has been pushing for granularity in their operating system. This means, the operating system itself would be able to set limits on processor utilization and memory space
    Why use a HyperVisor for that?
    For true isolation, and the ability to run multiple guests with different OSs with consistent performance not dependent on a company seeking a profit (MS/Windows)? Am I the only one that finds it humorous that MS has just started toating "granularity"...sorry couldn't help myself

    Quote Originally Posted by Yash-JH View Post
    It is debate-able, even in the Linux front, that XEN's HyperV can do a better job at process, IO and memory scheduling then the Linux kernel. In one study I read, cache misses were far more common on XEN, compared to a Linux Kernel - suggesting that XEN may not be doing the most efficient job in process scheduling. I'd argue the same would apply to memory and disk I/O. Let us think of it this way - the Windows or Linux kernel has direct access to the system's process queue, and can choose the best way to schedule usage of the CPU or the disk. With a HyperVisor such as XEN in between, alot of this is hidden from it, and it has to decide what Operating System rather than process to schedule first (please correct me if I am wrong).
    In all fairness, this is truly debatable. There is has been, and to this day is ongoing optimization with xen's scheduling. Which study do you speak of? This is pretty bold statement, and I would be interested to see the extent of the research.

    Quote Originally Posted by Yash-JH View Post
    Hence, XEN will always represent an overhead compared to OS-level virtualization. Yes, there are advantages to this - it provides complete OS-level isolation. BUT, I would argue, with Operating System design becoming more granular, these sand-boxes could also be created on the system itself, without the overheads of a 3rd party HyperVisor. This is the philosophy of OpenVZ or Virtuozzo. And it too, IMO, is Real Virtualization.
    It depends what on one's definition of "real virtualization." In my eyes Virtuozzo will always be a doctored up jail/chroot environment. It is good at what it does, and certainly has a place in the market. At the same time, soft allocation of resources certainly leaves the door open for the class of overselling that this industry has been plagued with. Thankfully Parallels charges decent coin for Virtuozzo (surprise surprise here eh? ), keeping a good amount of the kiddy hosts from getting their hands on Virtuozzo.
    Last edited by johringer; 12-22-2009 at 03:31 AM.

  24. #49
    The most important thing is, customer choose Xen more than OpenVZ.
    Why? This is because of Xen standalone kernel, RAM and applications.

    We have received a lot of Xen Linux VPS request from our customers.
    Then start to offer Xen Linux VPS services to our customers.

  25. #50
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    Quote Originally Posted by cartika-andrew View Post
    even if this were true, a customer is still reliant on their upstream to not oversell the hell out of the server and leave them competing for resources..



    Isnt this what managed services are supposed to cover? I know if we asked our clients to install their own kernel or configure swap, they would likely look at us pretty funny - doesnt mean you can just neglect the benefits of real virtualization and attempt to claim that somehow there is an advantage to software level virtualization because a customer doesnt need to install their own kernel.. sure, its easier for the provider to manage this way - but, I am not so sure its better for the clients - I guess it depends on what customers are after.. but, to use your cost-benefit analysis - it would not be overly difficult to present an alternate analysis here..

    Doesn't help when a well known managed vps provider has this kernel running:

    2.6.9-023stab044.11-enterprise #1 SMP Sun Sep 30 12:15:39 MSD 2007 i686 athlon i386 GNU/Linux

    which doesn't patch for http://cve.mitre.org/cgi-bin/cvename...=CVE-2009-3547
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