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  1. #1

    Public Cloud: Xen vs. VMware

    I'm looking at Rackspace, EC2 and vCloud Express (Terremark & Virtacore) marketing messages and trying to figure out which cloud is really better (excluding pricing). Are the underlying virtualization platforms all that different? My gut tells me that since VMware is more of an enterprise product that it should be better than open source Xen. However, I don't hear of many people using vCloud Express so am I missing something? Why would Enterprises use VMware if Xen is better or am I mixing apples and oranges?

  2. #2
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    Apples and Oranges. You really hear more about Xen stuff and the big guys like Amazon and Rackspace because those are the web scale type clouds. Reality check is that while they are nice and all, there is a much bigger world out there that isn't cloud based.

    Xen has some great features, but VMware is far more geared towards performance. Things like DRS, etc all really make a difference. For what it's worth, my personal stuff is spread between Steadfast and Terremark.
    I <3 Linux Clusters

  3. #3
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    Quote Originally Posted by x86brandon View Post
    Xen has some great features, but VMware is far more geared towards performance. Things like DRS, etc all really make a difference. For what it's worth, my personal stuff is spread between Steadfast and Terremark.
    I also see people that use VMware want much more control of the configuration of their VMs, network, etc. It's really for control freaks, which isn't necessarily a bad thing.

    VMware has also dominated the Enterprise market early on and has a lot of staying power, especially since they have numerous supporting products that make the platform that much more powerful, such as local VMs running on Workstation, Fusion, Server, ACE, etc.

    You will also find that cascaded snapshots, Storage vMotion, and resource pools are very well done in VMware compared to the other hypervisors. In vSphere 5, providing for complete control over CPU, Memory, Disk, and now Network resources across a number of VMs in the pool.

    Many of these features are unknown to the public who has never used VMware's products and rather only used the typical web-based interfaces to public cloud providers. Like Brandon said, there is a whole world out there outside of this market that is looking for some of these features that simply aren't available yet on other platforms (the keyword is "yet"... and I hope is becomes "soon" . Competition is a good thing.

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  4. #4
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    Personally I like Xen better due to being "impossible" to oversell. Well - there are ways to do it anyway, but it is a platform that is designed not to be oversold.

    Also, Xen is much more like a dedicated server, so you don't run into issues like software not compatible.
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  5. #5
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    Xen was made for Grid computing, VMWare mostly focussed on Enterprises.

    So where's the differences?
    Grid computing required scaling over hundreds of physical servers even in the earliest deployments and often running CPU or IO intensive HPC workloads. As the users were mostly on a university playground level, perfect ressource isolation (from performace point of view, not security)

    Enterprises loved to consolidate 200-400 useless Windows servers onto one 4node ESX Cluster. They required perfect ressource isolation, builtin solutions for snapshot backups and anything that avoids downtime! Stuff like online storage migration was a MUST for them, whereas it didn't matter as much if they got 50MB/s or 100MB/s network throughput.
    They didn't care half as much if VMWare introduced a 30% overhead if it helped them to save 100s of servers.

    So, even now, VMWare has much easier ways to achieve HA or configure management stuff, but isn't going to flyyyyyy in performace. Just that you might still see better performance at the end of the day as it's much more robust against abusive users.

    And Xen is (in the right hands) a lot more flexible and a paravirt domU is the only kind of virtualization you can use if you mean real business in performance terms.

    2 years ago some team at $oldjob asked for an eval of running Oracle on VMWare instead of bare metal. If was obvious where they'd end up when creating the ext3 filesystems took over 50 minutes...

    So if the systems in that cloud will be running at high CPU load and high IO rates, you'll need Xen.
    If you expect overall usage to be in the < 10% areas CPU wise and if there is a really powerfull storage backend, if you want awesome features for grouping customers into SLA groups (bronze gets less cpu shares than gold), then VMWare is a lot more powerful.
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  6. #6
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    Quote Originally Posted by Slimasaurus View Post
    Are the underlying virtualization platforms all that different? My gut tells me that since VMware is more of an enterprise product that it should be better than open source Xen.
    As most of the previous posts have mentioned, VMWare is your Ferrari. Xen is very good -- open source and enterprise versions -- but they're not quite as good as VMWare. They've been focused on performance from the inception of their company and it shows in the real-world use cases of their product.

    Some of the things that make a 'cloud', such has DRS, high availability, hot migration across hosts, have been pioneered and perfected by VMWare. You won't go wrong with VMWare-based public clouds unless they are very poorly engineered.

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  7. #7
    Quote Originally Posted by daveg01 View Post
    As most of the previous posts have mentioned, VMWare is your Ferrari. Xen is very good -- open source and enterprise versions -- but they're not quite as good as VMWare. They've been focused on performance from the inception of their company and it shows in the real-world use cases of their product.

    Some of the things that make a 'cloud', such has DRS, high availability, hot migration across hosts, have been pioneered and perfected by VMWare. You won't go wrong with VMWare-based public clouds unless they are very poorly engineered.

    Best,
    Dave
    Dave with all due respect your Ferrari comparison sounds like a bit like marketing speak. Performance seems so very subjective, in an earlier post someone inferred that VMware's overhead will hurt performance while you say it will be fine. IMO, it's probably a wash or does DRS make that much of a difference?

    The HA option that VMware providers offer sounds compelling. One said that if a node that is running my instance fails my instance will move to a working node. That sounds cool, does EC2 have similar capabilities? I couldn't find anything similar on their site, my guess is I'd have to pay for redundancy. However, I didn't see any vCloud providers offering auto-scaling like EC2.

    It sounds like a feature war between public clouds to me am I wrong?

  8. #8
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    Quote Originally Posted by Slimasaurus View Post
    Dave with all due respect your Ferrari comparison sounds like a bit like marketing speak.
    That's fair . I'll be more objective with regard to feature set below.

    Quote Originally Posted by Slimasaurus View Post
    The HA option that VMware providers offer sounds compelling. One said that if a node that is running my instance fails my instance will move to a working node. That sounds cool, does EC2 have similar capabilities?
    Yes, IMHO HA is really, really cool. Basically you're talking about minutes of downtime in the event of a host failure. It's essentially just long enough for a reboot. You can also tweak the HA settings based on the heartbeat of the actual VM, or an application within the VM.

    Another compelling VMWare feature is storage IO control, which allows you to basically guarantee slices of access to the underlying storage. This is great for keeping your IO consistent across various nodes even under high load.

    There may be other hypervisor platforms that come close to VMWare performance, but it's kind of like the old Cisco saying, "Nobody ever lost their job for recommending Cisco equipment." IMHO the same goes for VMWare. Though they may not have gotten a raise, since the cash probably went to licensing costs .

    Best,
    Dave

  9. #9
    Quote Originally Posted by daveg01 View Post
    You won't go wrong with VMWare-based public clouds unless they are very poorly engineered.

    Best,
    Dave
    How can I tell if one of the VMware providers are poorly engineered? What questions should I ask? What do I not want to hear?

  10. #10
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    Quote Originally Posted by lakridserne View Post
    Personally I like Xen better due to being "impossible" to oversell. Well - there are ways to do it anyway, but it is a platform that is designed not to be oversold.

    Also, Xen is much more like a dedicated server, so you don't run into issues like software not compatible.
    Incorrect. VMware and Xen both can be oversubscribed and both present themselves the same way.
    I <3 Linux Clusters

  11. #11
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    Quote Originally Posted by wartungsfenster View Post
    Xen was made for Grid computing, VMWare mostly focussed on Enterprises.

    So where's the differences?
    Grid computing required scaling over hundreds of physical servers even in the earliest deployments and often running CPU or IO intensive HPC workloads. As the users were mostly on a university playground level, perfect ressource isolation (from performace point of view, not security)

    Enterprises loved to consolidate 200-400 useless Windows servers onto one 4node ESX Cluster. They required perfect ressource isolation, builtin solutions for snapshot backups and anything that avoids downtime! Stuff like online storage migration was a MUST for them, whereas it didn't matter as much if they got 50MB/s or 100MB/s network throughput.
    They didn't care half as much if VMWare introduced a 30% overhead if it helped them to save 100s of servers.

    So, even now, VMWare has much easier ways to achieve HA or configure management stuff, but isn't going to flyyyyyy in performace. Just that you might still see better performance at the end of the day as it's much more robust against abusive users.

    And Xen is (in the right hands) a lot more flexible and a paravirt domU is the only kind of virtualization you can use if you mean real business in performance terms.

    2 years ago some team at $oldjob asked for an eval of running Oracle on VMWare instead of bare metal. If was obvious where they'd end up when creating the ext3 filesystems took over 50 minutes...

    So if the systems in that cloud will be running at high CPU load and high IO rates, you'll need Xen.
    If you expect overall usage to be in the < 10% areas CPU wise and if there is a really powerfull storage backend, if you want awesome features for grouping customers into SLA groups (bronze gets less cpu shares than gold), then VMWare is a lot more powerful.
    Very incorrect, VMware has a number of features more than Xen, it's more matured and has better support for things like iSCSI, etc. Performance wise, I have seen VMware to be faster.
    I <3 Linux Clusters

  12. #12
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    Quote Originally Posted by Slimasaurus View Post
    Dave with all due respect your Ferrari comparison sounds like a bit like marketing speak. Performance seems so very subjective, in an earlier post someone inferred that VMware's overhead will hurt performance while you say it will be fine. IMO, it's probably a wash or does DRS make that much of a difference?

    The HA option that VMware providers offer sounds compelling. One said that if a node that is running my instance fails my instance will move to a working node. That sounds cool, does EC2 have similar capabilities? I couldn't find anything similar on their site, my guess is I'd have to pay for redundancy. However, I didn't see any vCloud providers offering auto-scaling like EC2.

    It sounds like a feature war between public clouds to me am I wrong?
    No one does HA as good as VMware right now. Fault tolerance + HA turned on and a server dies and you will never even notice. Not even a dropped ping.
    I <3 Linux Clusters

  13. #13
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    I canīt say much about the technical backgrounds of Xen and VMWare,
    but can tell you about my experience as a user of a VMWare server.

    Sometime ago I applied for a free trial of a cloud server based on VMWare
    and ended frustated because it required me to use and old version of Firefox
    or Internet Explorer to manage its interface, that by the way wasnīt easy to use.

    I donīt know if this has changed lately.

  14. #14
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    There both very good packages, however they both scale in very different ways.

    For example, as you grow a cloud infrastructure things like VM workflow and storage IOP can become a massive issue for large vitalized environments. Your storage can only provide a certain amount of disk operations a second (iops) and if you come close to reaching this limit the whole cloud will grind to a halt.

    Vmware have put a lot of development into monitoring and managing aspects like this, and actually allow you to restrict the amount of IOP a singe VM can use. However unless you purchase Xen from citrix (by which i mean, you not using the free version) your not going to be get any features like these.

    I have come across clouds that have IOP issues and trust me. Its a very bad place to be.

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