Xen and UML are two other virtualisation techniques, like Virtuozzo, the main difference being they are free. They also virtualise in different ways by creating more of a 'real' virtual machine than Virtuozzo.
To put it simply they're a lot more straightforward than Virtuozzo, you have a simple VM that runs your OS with exact limits specifically for your VPS, rather than shared and burstable memory usage, etc, etc. Performance is much more predictable.
Out of the two, Xen is the best performing, infact I'm not 100% sure on this but I've heard it offers better direct throughput than Virtuozzo. UML unfortunately suffers from CPU and I/O throughput problems, and is considerably slower than any other VM solution.
I can't give you exact info on what servers use what, because each host does it differently, if you run "cat /proc/cpuinfo" and "df" from a shell and post the results here, I can probably tell you what system the VPS uses.
You can find more out about these VM solutions on the following sites:
I think the first thing to understand is there is no "perfect" solution for VPS's..all have their strong and weak points.
If you are just starting with linux...and what to get up to speed quick using not just one distribution..but several easily..then UML is for you. THese VPS's tend to be slower than Xen and others..but are fairly inexpensive and can be configured with several bootable partitions that you can switch back and forth from quite easily. I have had UML servers with:
Based on our experience hosting both Xen and UML based VPSs I'd compare them as follows:
- different implementation (hypervisor vs. user process; though this isn't something that the end VPS user 'sees')
- Both are good, solid, reliable, Open Source technologies. You'll get root access, your own distro and the flexibility to do pretty much whatever you need.
- Functionally you'd be hard pressed (as a VPS user) to notice whether you were running one or the other (without 'cheating' by looking in /proc or at the /etc/fstab device names).
- Xen runs faster (in benchmarks and in day to day use)
Internally we have switched to doing new setups on Xen, primarily because of the performance improvment.
I think we will slowly see UML phased out and the 2 major technologies will be Virtuozzo and Xen. Virtuozzo now supports Windows and almost any Linux distro. Xen is backed by many large companies, but in the end it will probably always be more expensive for what you get. 2.0 is definitely rock solid, 3.0 promises many awsome new features to make it usable in large (read: Fortune 500 / Global 1000) companies.
Matt Ayres - togglebox.com
Linux and Windows Cloud Virtual Datacenters powered by Onapp / Xen
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