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Overselling Explained: OpenVZ v. Xen

Overselling Explained: OpenVZ v. Xen

marrcomarrco Member
edited October 2012 in General

just found a great article about overselling on WHT: http://www.webhostingtalk.com/showthread.php?t=1193035

hope the next one will explain why abusing your vps with infamous DD test just hurts your neighbors and doesn't work as a real-world quality or performance indicator.

thoughts?

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Comments

  • Been posted before on LET, but doesn't hurt to post it again. People need to know :D

    D4jsp - Where virgins roam free
  • High prices on XEN are some sort of a scam in relation to overselling? Good to know.

  • same question here...why Xen is more expensive than OpenVZ if Xen is no faster and still can be oversold as OpenVZ...must be some advantages to justify the higher price...more stable/reliable?

    A list of VPS Providers with their Data Center information: vpsdb.net

  • TazTaz Disabled

    @CoolMoon said: same question here...why Xen is more expensive than OpenVZ if Xen is no faster and still can be oversold as OpenVZ...must be some advantages to justify the higher price...more stable/reliable?

    While 10000's of inactive/idle ovz container has no affect on the main node, inactive xen and kvm will still have affect and thus, you can not fit the same number of ovz container per node comparing to XEN/kvm VPS (To those who likes to oversell in real way). It shouldn't affect providers who claims not to oversell. Then again, why not take the money if people are willing to pay extra ;)

    Time is good and also bad. Life is short and that is sad. Dont worry be happy thats my style. No matter what happens i won't lose my smile!

  • why Xen is more expensive than OpenVZ if Xen is no faster and still can be oversold as OpenVZ

    Maybe because people will pay a premium to actually control all the processes within their VPS? I mean, as opposed to OpenVZ's prohibition on many aspects of system configuration.

    Thanked by 1connercg
  • MaouniqueMaounique Member
    edited October 2012

    @swsnyder said: prohibition

    It is not only prohibition, it is mostly lack of features. OVZ is emulating too many thing to look like a real emulation if you get my pun... For example vserver is honest, you get a few processes on a big server and your little share of disk and memory. OVZ has to load TUN/TAP in order to emulate NICs for example and that is a really-really bad design. Other than that, OVZ is faster in similar conditions and works like a champ for most hosting cases. Xen is more or less a full machine emulation, much closer to KVM than vserver. You can run all things you can run on bare metal with few exceptions you probably dont need (even tho usb has been added lately and even passthrough and other things you would most likely need on a desktop, not server). M

    Who's General Failure, and why is he reading my drive A: ?

  • vdnetvdnet Member
    edited October 2012

    @CoolMoon said: same question here...why Xen is more expensive than OpenVZ if Xen is no faster and still can be oversold as OpenVZ...must be some advantages to justify the higher price...more stable/reliable?

    As being the author of the WHT post, I thought I would chime in.

    Xen can be more expensive for a variety of reasons, but really it shouldn't be much more expensive. From my experience as we used to offer both Xen and OpenVZ:

    1. The Xen market is far less saturated, less competition, so hosts can charge more and get away with it.
    2. Xen is less efficient, and you can't run as many servers without degrading performance. The Xen dom0 can take up a lot of RAM and system resources itself. So you have to pay for the wasted resources. (EDIT) But the overhead of Xen is what allows users to run their own kernel and have more control.
    3. Xen requires more system administration time. OpenVZ is much easier to both setup and maintain.

    I'm not speaking against Xen, Xen is a great technology and should be valued as well. For some things Xen is obviously better and gives the user the full control over their own kernel and modules. However, for what most users use a VPS for (web hosting), OpenVZ works great and is more efficient/higher performing as long as the host maintains the nodes properly.

    ByteOnSite :: Affordable cloud VPS, 7 years of experience

    Thanked by 1marrco
  • @vdnet said: However, for what most users use a VPS for (web hosting), OpenVZ works great and is more efficient/higher performing as long as the host maintains the nodes properly.

    I find it quite difficult to run web hosting on OpenVZ - usually the web server chugs all the memory over time (creeping into your burst memory) until it finally gets cut off by openvz.

    The problem with using OpenVZ is that the system doesn't understand what is actually your memory and what is burst. This makes, in my eyes, OpenVZ borderline useless for web hosting.

  • MaouniqueMaounique Member
    edited October 2012

    @vdnet said: I'm not speaking against Xen, Xen is a great technology and should be valued as well. For some things Xen is obviously better and gives the user the full control over their own kernel and modules. However, for what most users use a VPS for (web hosting), OpenVZ works great and is more efficient/higher performing as long as the host maintains the nodes properly.

    Thank you. This is something that I tried to get across many times with various degrees of success. Every virtualization (even tho OVZ is not techically virtualization) has + and - it all depends on the intended use. Ppl make their choice thinking about how easy is to oversell one or the other and base their decision on that mostly. An hones host will maintain good performance no matter what kind of server while a crook will oversell everything, there are very few ppl that don't know to oversell something else than OVZ, I think only the summer hosts that use google as their "proven experience".

    @littleguy said: The problem with using OpenVZ is that the system doesn't understand what is actually your memory and what is burst. This makes, in my eyes, OpenVZ borderline useless for web hosting.

    That is very strange, I havent experienced that on any host with .32+ kernels. It is true, I am not running heavy servers with tomcat and whatnot, however did my share of java and apache (standalone) and the servers run for months without any problem. Maybe it is some module you run... M

    Who's General Failure, and why is he reading my drive A: ?

  • vdnetvdnet Member
    edited October 2012

    @littleguy said: I find it quite difficult to run web hosting on OpenVZ - usually the web server chugs all the memory over time (creeping into your burst memory) until it finally gets cut off by openvz.

    The problem with using OpenVZ is that the system doesn't understand what is actually your memory and what is burst. This makes, in my eyes, OpenVZ borderline useless for web hosting.

    You don't seem to understand how OpenVZ works. Burstable memory is just a phrase for privvmpges, the true hard limit for memory. OpenVZ was designed to work with more privvmpages than your guaranteed RAM.

    Your host shouldn't punish you for using burstable memory if your used RAM (physpages) is in fact lower than your guaranteed amount. You should also always be able to use burstable RAM according to OpenVZ.

    Oomguarpages is the out of memory limit which some people refer to as "killing processes", but oomguarpages measures used memory, not allocated memory (like privvmpages) and will only start killing processes if the entire physical node is out of both RAM and SWAP. A proper host should never run out of RAM and most certainly never run out of both RAM and SWAP.

    ByteOnSite :: Affordable cloud VPS, 7 years of experience

  • JarJar Member

    A real provider uses LXC.

    image

  • sleddogsleddog Member
    edited October 2012

    @vdnet said: Xen requires more system administration time. OpenVZ is much easier to both setup and maintain.

    Finally you've hit the nail on the head.

    Any Tom, Dick or Mary can easily setup an OpenVz node. Heck, even I can do. Any number of containers can be created and sold. It's just numbers; there's no requirement for them to add up in any way. OpenVz is the easy entry point into the "VPS Provider" business. Dozens -- hundreds -- have taken it, with the vision of easy profits dancing in their heads. Inevitably they fail due to inexperience and incompetence.

    I've been using VPSs for over 10 years, have had experience with a lot of difference providers, and there's one thing I'll say: I've never encountered an incompetent Xen host.

    Buy a Xen plan today and behind the order form there will be people who know what they're doing. And for the end-user, that's what makes all the difference in the long term.

    Yes, there are good and highly competent OpenVz providers as well, but the only real way of distinguishing them is to buy-and-try. And that buying only feeds the steady stream of inexperienced, incompetent wannabe-hosts using OpenVz, and further poisons OpenVz's credibility as a technology.

    Thanked by 1marrco
  • I have nothing to add but to confirm that I use OpenVZ and that I oversell.

    :-)

    Ransom IT | ɹǝpun uʍop sdʌ | vps down under | KVM in Sydney and Adelaide | OpenVZ in Sydney and Melbourne
  • @jarland said: A real provider uses LXC.

    Hmm, no doubt LXC has potential, but OpenVZ has more active development and is based on Virtuozzo.

    ByteOnSite :: Affordable cloud VPS, 7 years of experience

  • @Oliver said: I have nothing to add but to confirm that I use OpenVZ and that I oversell.

    :-)

    There's nothing wrong with overselling.

    The problem comes with over-provisioning, and being either incapable or unwilling to deal with the issues that inevitably arise.

    From what I've read, you're one of the good guys :)

  • @Taz_NinjaHawk said: Then again, why not take the money if people are willing to pay extra ;)

    I really like this comment..

  • I don't look at virtualization technologies from the point of view of overselling anymore, because in some way everything can be oversold, wetter it's RAM or I/O resources or CPU resources.

    I look at them for their merits and limitations: - OpenVZ - positives: basically no overhead since every VM uses the same kernel on the node, therefore extremely fast - drawbacks: because of it's architecture it is more closely tied to the host node and therefore the isolation isn't always that great, and you can't anything else but Linux on it - KVM - positives: as close as it gets to a real server, good performance, virtio drivers help, can run anything that the host CPU architecture can... so if it's X86 any X86 OS will work on it. Basically it will run anything that's x86 on x86. - drawbacks: has the worst control over CPU resources out of all 3 major virtualization technologies and has poor I/O control. - Xen HVM - positives: can't really think of any these days... other than it can be deployed on the same node with Xen PV. - negatives: let me put it this way: sometimes the guest will run fine, most times it won't. It's like playing the lottery, just cross your fingers and hope it boots... - bottom line: Just pick KVM over this garbage, you will be better off in the long run. - Xen PV - positives: excelent granular CPU resource control, distributes I/O resources reasonably (unless you're on Xen 3.x then yuck), just as easy to create templates for an migrate as OpenVZ, really good integration with SolusVM, just like OpenVZ. Extremely low overhead, or slightly higher than OpenVZ because there is no hardware emulation involved, everything is paravirtualized. - negatives: it loads a bare-metal hypervisor before it loads the Linux Kernel for dom0, both of which eat up RAM, and the hole idea of dom0 and domU is ridiculous, you need to make sure that every kernel in each guest OS is paravirtualized (has Xen support built in), if you load the dom0 kernel in domU it won't save you any RAM, you can't do custom partitions like with KVM, and there is probably more but I will stop here. - bottom line: I like Xen allot and customers love it, but I like KVM even more, and as soon as the last few drawbacks and bugs are completely solved I will give Xen a swift kick in the ass and got 100% with KVM because it is easier to support a single virtualization technology.

    As far as the overselling myths around OpenVZ, they are just that: myths. It is all up to the provider how good and how well they take care of their servers. Customers are more knowledgeable than ever before so it's hard to oversell anything and last in this business. Just my 2 cents.

    Thanked by 2Jack SimpleNode
  • JarJar Member

    @vdnet Joke, it's a terrible choice for security ;)

  • TazTaz Disabled
    edited October 2012

    @sleddog Just thought I would add, our buddy Randy was using xen ;)

    Time is good and also bad. Life is short and that is sad. Dont worry be happy thats my style. No matter what happens i won't lose my smile!

  • RandyRandy Disabled

    calling me ;-)

  • @vdnet said: However, for what most users use a VPS for (web hosting), OpenVZ works great

    This is the key sentence and need more detail : for PHP web hosting. I will not put my openfire server in openvz anymore.

    ...............

  • @vpsnodebox really good summup

    VirtualSRV - OpenVZ Unmanaged VPS
  • OpenVZ : Bicycle XEN/KVM : Car

    Like that maybe? Both have positive/negative side..

    "I Always Happy ! The Secret Is, When Something Bad Happens, I Always Yell : Eeee... Macarena !!" :D

  • @Rikimaru90 said: OpenVZ : Bicycle XEN/KVM : Car

    Like that maybe? Both have positive/negative side..

    Any explanation for your odd analogy?

    ByteOnSite :: Affordable cloud VPS, 7 years of experience

  • @Rikimaru90 said: OpenVZ : Bicycle XEN/KVM : Car

    More like SUV vs Van.

    ~ Jimmy VortexUnit. Who likes poptart.cats?
  • Ooo. Shitty Analogy time.

    OpenVZ is a cardboard box, Xen is a Jail.

    You can cram more cardboard boxes on a piece of land when compared to Jail cells, as they take up less room, and you can just compress them (oversell) to fit more into the same space.

    Xen (the jail), on the other hand, takes up more space while it's interior space is the same (dom0 eats resources, while resources available to VPSes are the same.).

    I have no idea what I just wrote.

    SimpleNode | Minecraft and VPS Hosting | KVM and OpenVZ | Dallas, TX and Phoenix, AZ | PayPal and BitCoins accepted

  • To continue the shitty analogies...

    OVZ is like a live-in landlord (shared kernel)...each day you wake up thinking "has my room just bigger"...but later in the day things are feeling a bit more cramped (the advert did say "cosy").

    KVM the landlord lives next door and tends to announce his visits...but ultimately he has keys so could slip in if needed...

    Xen is similar just the landlord has been through a bunch of divorces ;)

    "Go cheap on rarely used things"

  • These shitty analogies are good. Keep them coming!

    Ransom IT | ɹǝpun uʍop sdʌ | vps down under | KVM in Sydney and Adelaide | OpenVZ in Sydney and Melbourne
  • eastoncheastonch Member
    edited October 2012

    OpenVZ: Wife Xen/KVM: Mother-in-law.

    Joke? Not getting pleasure from either of them. :')

  • ZenZen Member

    WTF IS WRONG WITH EVERYONE

  • @Zen welcome to LET.

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