Linux Magazine has an extensive article the technical details and motivation behind Xen by one the developers.
Xen, a new, high-performance x86 virtualization system
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That article was from October, they have even made another release since then, along with new info that Xen appears as if it will be included in the next kernel release (after 2.6.10).
This is great inovation but what is it for again? There was mention but waht are the current pros and cons.
I’m concerned this a another layer of buggy complexity for the end user. Academically cutting edge to be sure. Yet, were’s the “beef” in laymans terms?
Can I run sandboxed OS’es of my choice and instantaneously flip between them?
Is it not better to get one OS working maturely? Is there a huge advantage over the dred simple duel boot? Is the down side worth it?
Clarity needed.
The biggest advantages are for hosting and development. The ability to add a numbers dedicated servers all running on one piece of hardware, without the resource hit that the existing VM implementations sack you with. With Xen 2.0 they have added the ability to move these VM’s from one machine to another.
For my company this is very exciting as we never seem to have enough hardware around for development projects. This will enable us to add dedicated servers as needed, and then just delete them when the process is complete. Or if required, we can actually archive that particular dev server, and keep it on file so to speak.
I’ve never seen the advantage of this over just improving the native OS’s (Linux, in this case) ability to checkpoint and restore processes — and perhaps improve the sysadmins ability to manage processes.
The running of multiple OS’s to accomplish this seems practical, but so incredibly brute-force and nasty to me.
The thing that sucks about Xen though is that you need to tune an operating system in order to run on Xen.
Unfortunately, the real problem is that to do *TRUE* virtualization on Intel, you need to tune your Intel OS. Thankfully, something like Linux, FreeBSD, etc (OSS), can be modded to remove/work-around the reliance on non-virtualizable Intel instructions.
On many other chips (POWER, PowrPC, even ARM, I believe), virtualization is much easier….
You’re looking at this problem from the wrong perspective. Hypervisor technologies, like Xen come from the IBM mainframe world, not the desktop world.
Can I run sandboxed OS’es of my choice and instantaneously flip between them?
Well yes, but the general idea is that you have several servers running on the same hardware. cutting hardware cost and dynamically sharing resources between the different servers (‘partitions’ or ‘domains’)
In a corporate environment not only does the hardware maintenance cost decrease but also the ‘floorspace’ used (most of the time a valuable resource.)
Is it not better to get one OS working maturely? Is there a huge advantage over the dred simple duel boot? Is the down side worth it?
No. Look at IBM with their P-series it supports several partitions now with AIX and Linux and in the future also with OS/400’s descendant. Corporate environments are fragmented, heterogenic, it makes sense to accomodate this.
Clarity needed.
Conclusion : you wont see what problem this solves until you ask the right question.
For my company this is very exciting as we never seem to have enough hardware around for development projects. This will enable us to add dedicated servers as needed, and then just delete them when the process is complete. Or if required, we can actually archive that particular dev server, and keep it on file so to sp
Yes , you know you can already do this with P-series / AIX though the cost might be prohibitive if you are a really small company. You can easily set up new partitions, dynamically share resources between partitions, all on the same machine. And restoring the machine from a system backup (mksysb) by tape or over the network is easy.
It should be noted sun has similar, though less functional capabilities in its latest offering.
Yes, I was aware of this, and we are a small company (currently 15). Xen brings to us the functionality that generally only the larger companies have been able to afford historically.
I think QEMU is fast enough and more advanced then this one…
you are kidding…
I think QEMU is fast enough and more advanced then this one…
Maybe, but can you run servers inside it? I thought it had a built-in “firewall” which only allowed outgoing connections.
Btw, NetBSD runs on Xen, of course 😉
How does it load share between the different virtual maschines? That is, if a program on one vm does a
while(true)
fork();
How does tha effect the other vm running on the same cpu?
That is: Can it share a single cpu so that each vm get an equal share of cpu cycles, independent of the number of tasks running on each vm.
I know that Xen can run other OS’s, but they have to be modified first, but if you were to use Xen to run linux on linux what is the difference between this and User Mode Linux?