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I’m looking for a new server at the moment and a fitting virtualization solution. On my recent server I’m using VMware server but don’t what this one anymore as it is very very slow.

I have the opportunity to work on a cluster which is using Proxmox with OpenVZ which is amazingly fast. How does Xen as DomU compare to that? Which one would you recommend?

The new machine’s going to be a Core i7 with 12 GB RAM. I’d like to either use Debian 6 or Ubuntu 10.04, but I’d prefer Ubuntu. Debian 5 is too old meanwhile and I hate using backports. The same’s for the guest systems, I’m not planning to use any Windows or something like that on this machine. So the disadvantage of not having the possibility to use KVM is ok.

I found this thread here regarding this matter but it’s pretty old, so I’d rather ask again ;-).

http://serverfault.com/questions/12110/which-virtualization-platforms-should-i-choose-xen-or-openvz

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I'd wonder why the VMWare system is slow. Is there an existing bottleneck that could be addressed? Is it happening because of a particular application? If you want to change platforms that's one thing, but if there's an underlying problem with the applications you're using or the server, a new platform may not address it (although you're getting a new server that could mask the issue) –  Bart Silverstrim Oct 12 '10 at 9:47
    
I already posted a question regarding the slowness of VMware a few months ago, no one could help. When logging in in one of the VMs via SSH it takes between three and eight seconds till the login is completed. That’s much too long. The services I’m running are ok, but not fast. When working on the native system outside the VM the server performs much better. The machine is not that fast, it’s a Athlon64 X2 5.600+ with 4 GB RAM. –  Ulf Klose Oct 12 '10 at 15:21
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6 Answers 6

up vote 4 down vote accepted

I am a fan of OpenVZ. I am also a Proxmox user.

OpenVZ is "just" a hardened chroot (with fine grained control and networking). The kernel is the same in the "containers" and on the host itself.

OpenVZ is lightweigth because of its design. It works perfectly fine as long as you need linux guests only. If your hardware supports hw virtualization you can use KVM (which is also in Proxmox) and you can do "full" virtualization and run wider range of operating systems.

I would not recommend Xen. You can get most features with KVM which is much more easier.

UPDATE

@ulf: In performance openvz is way better because there is almost no performance overhead. It is native system calls with a few more "security check". But as I said if the guest is not linux it is not an option. If one wants sophisticated networking it is doable, but it can be a pain.

When using Xen there is another layer (the hypervisor itself) involved which just passes over most of the calls verbatim most of the time, but does some translation/emulation for the others.

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What about Paravirtualization? Xen supports that, how fast is that compared to the OpenVZ performance? –  Ulf Klose Oct 12 '10 at 15:06
    
I made an update. Also see jlliagre's answer about performance. –  cstamas Oct 12 '10 at 18:26
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Proxmox is very good IMO, and has a lighter-weight implementation of libvirt than other KVM platforms.

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I have no specific experience with OpenVZ but am quite familiar with Solaris Zones which are similar in concept. OS level virtualization (Solaris Zones, Linux OpenVZ, BSD Jails) is inherently much faster and lightweight than any hardware level virtualization (vmware, kvm, xen, virtualbox) as you haven't to run one OS instance per virtual machine. All processes have access to the native drivers instead of relying on virtualized ones.

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OpenVZ is lightest, followed by Xen and KVM/VMware are the heaviest.

On the other hand, I've had problems with OpenVZ (very flaky during NFS, not really isolated etc.) and Xen, while KVM is very simple and adequately performant.

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Your slow logins via SSH are potentially attributed to dns lookups. Try turning off useDNS in sshd and see if your login times improve. In addition to this, also turn off any ident lookups that might be affecting this.

I know this might be a stretch, but I've run into this problem many times on non-virtualized systems.

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Well, my VM environment is now completely OpenVZ, no problems with slow SSH logins so far. But thanks anyway for your thoughts :-). –  Ulf Klose Dec 5 '10 at 13:00
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