Slashdot Mirror
Xen Hacker Interviewed
Drawoc Suomynona writes "The Xen virtual monitor is a new generation virtualization software that enable running multiple OSes at the same time with unprecedented level of performances. Manuel Bouyer was recently interviewed about his work porting Xen to the NetBSD operating system. The interview touches on why some consider Xen to be so good, how hard it is to integrate such a software package into an OS, and more."
>Linux is STILL for fags.
That's right, real men use BSD.
no, Xen requires changes be made to the kernel of the guest operating system, this can't be done with Windows, it could possibly be done with OSX though
Your answer and more:
_ monitor)
http://en.wikipedia.org/wiki/Xen_(virtual_machine
$7.95/mo, 200 GB disk, 2TBxfer, MySQL, PHP, RoR.
As I understand, vmware does do some limited emulation, at least VGA and Network cards. Xen instead traps all attempts to access the real devices in the machine and schedules them so that each operating system still thinks that they have full access to all of the real equipment. This requires some special kernel hooks, and that's why things like Windows and OS X aren't fully supported.
Also, I've seen this story in at least 3 places and I don't think it's right to say anyone ported Xen to NetBSD, NetBSD was updated (It's not exactly a "port") to take advantage of Xen features. It's possible that patches were sent to the Xen team to make things work more smoothly, but it's hardly porting.
HitScan
Anyone know Xen compares to jails in, say, FreeBSD? I've managed to setup a jail before where you do a "make world DESTDIR=/jaildir" and then do a jail on that directory, which gives someone the appearance of their own entire operating system. Is Xen similar to this, but allowing for many different operating systems rather than just another instance of the same one?
Also, glad to see the BSD section is at least still around. I can't seem to get it to show up on the Sections list, regardless of how I set it up.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
I see a ton of comments about not being able to use Xen to run Windows inside Linux, but no information the other way around...
Can Xen run Linux apps on my Windows installation? I am currently using Cygwin for that, and it's working okay, but some of my favorite apps are being run through SSH from my linux box to make all this happen.
I do too much in Windows to even dual-boot the system... I'd spend as much time booting as I would working/playing.
"If you make people think they're thinking, they'll love you; But if you really make them think, they'll hate you." - DM
"Xen also offers virtual machine migration, where you freeze a Xen guest, move it to another machine and resume it there ... This also means that a similar environment for the guest has to exist on the remote system."
And if a similar environment is not available when it is moved, what happens to the state of the user? Would the hardware in use when the state is saved have to be exactly alike on the target machine?
Also, is the information retained on the backup until the full migration is completed and then deleted, or is deleting the backup during the migration optional, leaving a "frozen" and "restorable" state on the server? Is that a security risk if the workstation is compromised?
Stoned4Life
gen = new Random
Xen virtual machines can be "live migrated" between physical hosts without stopping them. During this procedure, the memory of the virtual machine is iteratively copied to the destination without stopping its execution. A very brief stoppage of around 60-300 ms is required to perform final synchronisation before the virtual machine begins executing at its final destination, providing an illusion of seamless migration. Similar technology is used to suspend running virtual machines to disk and switch to another virtual machine, and resume the first virtual machine at a later date.
(Quote from Wikipedia)
Reminds of when I was watching the old Max Headroom show, and Max would shuffle himself off of one monitor onto a display on a portable "processing unit" and somebody would pick him up and carry him away.
The higher the technology, the sharper that two-edged sword.
We hear from those anal retentive, perfecto BSD users again.
My understanding is that Xen does not require the guest OS to be changed if the hardware supports virtualization (Vanderpool or Pacifica, depending on your chip maker). That means that with the right chip (I'm not sure if Core Duo has it or not) you could run OS X as a guest OS (I assume the host OS still needs to have support, which may be done with a simple application running as root).
Comment forecast: Bits of genius surrounded by a sea of mediocrity.
so guest OSes that support that hardware can run with standard drivers. Xen creates a synthetic virtual device that's easier and more efficient to emulate than standard hardware. The downside is that there usually aren't any drivers for these virtual devices on most OSes since no one's written them yet. So if you go on Apple's web site and look for supported video hardware, you probably won't see Xen virtual video device. The other way of looking at it is Xen is the device maker and is supplying the driver directly rather than through Apple. And device makers don't always supply drivers for all OSes, at leat right away.
What I want from OS virtualization is to be able to run one guest OS on multiple hosts for redundency. I don't have (personally) much use for running multiple guest OSs on a host. I want to have a setup where if apache is in the middle of processing a request and a whole machine does, the request is still completed by the remaining machine. RAID1 for the whole damn machine. If you could do this will F/OSS on dirt cheap comodity hardware, the utility would be huge.
"You never know when some crazed rodent with cold feet might be running loose in your pants."
-Calvin
What? You like BDSM? Thanks for sharing, but... uhh... no thanks. Well, it probably is VERY manly.
The 'Net is a waste of time, and that's exactly what's right about it. - William Gibson
There's a dude who knows his stuff
Sure his code is interestingly enough
It will fulfill our wettest dreams
Taking multitasking to the extremes
Filling our machines with marshmallow fluff
11. Thou shall obey Da mighty Swing
Xen 3.0 on the newer Intel/AMD chips should be able to run Windows (or any other OS) without modification to the hosted OS.
Apparently the currently shipping CoreDuo machines do not have virtualisation enabled. See here.
I looked this up a while ago... Xen needs the HOST OS to be modified, at least with current CPUs. Fortunately, VMWare player if free as in beer, and it works. So, now I have a perfectly functioning Linux install which I couldn't do before (lack of WiFi support for my wireless chip). Xen is nice, but free VMWare is good and it works.
Solaris Zones...
Are here and they rock
And FreeBSD jails have been here forever and they rock.. They compare a lot better to Solaris zones then XEN does.
First difference: XEN runs virtual machines with possibly completely differet guest OSes, jails and zones run instances of their host OS as guests (often sharing the kernel).
Different purpose, different technology, tho with some incidental overlap (you could use both to create multiple 'virtual' environments on one piece of hardware)
VMWare ESX Server 3 (currently in beta) will probably get as close as you can to having live fault tolarant servers. By sharing a storage such as SAN or iSCSI, it is able to instantly take over when it detects the failure of another physical box and should not lose any sessions or data. The other cool thing is that it can dynamically move a running virtual machine to a less loaded physical server. Still, it is not running two virtual machines simultaneously like you've described.
Actually the solaris developers are planning on integrating xen into solaris and zones. So you could run a Linux zone that doesn't even know that solaris is running. Or, if you felt so inclined, another Solaris instance.
Which would completely rock. I already love zfs in opensolaris, the ability to install a linux distro into a zone with xen would make me super happy.
Then I can get gentoo and solaris all in one. (don't argue about why I want Solaris to be the master domain, it is personal preference. mainly because I could snapshot the linux zone using zfs and have a very easy way to back up/rollback, my mind boggles with the possibilites)
Sorry, resume your disorder.
Sun is said to be busy on XEN support for Solaris.
Just having that will be enough to run Solaris and Linux at the same time, and other then a possible management interface I really wonder what zones have to do with this all, if you have any more information it would be appreciated.
It requires changes to the guest Kernel. Dont expect microsoft to do this for us, they have nothing to gain by doing that.
---- Booth was a patriot ----
Yeah, but does it run linux?
Oh wait......
The truth shall always be free: Boris Floricic is Tron.
Intel makes the chips. They have said quite clearly that the chips do support VT. People have displayed dmesg's showing that the CPUs do in fact report that they support it. Its just that some companies are shipping shitty boards with the functionality turned off, that doesn't mean that the CPUs don't support it.
. pdf
http://appleintelfaq.com/images/intel_vt_response
I was not aware of this fact, last i had checked for the ability to do so it still required changes to the guest OS, according to their fact though it is not yet completed for using hardware virtualization.
On hardware that supports it (new Intel and AMD chips do), Xen does not need changes to the guest operation system. So you might be able to run OS X and Windows at the same time.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
And also, the Cambridge guys did come up with a Windows XP port for their own academic purposes, but they obviously cant release it for licensing reasons, etc.
-- listen to interesting music, support independent radio... WPRB
Xen is much faster than Qemu. But it can only run OSs that have been modified. In contrast Qemu should be able to run any intel arch OS. It has been awhile since I looked in at this, but I thought that Qemu was being modified to run under Xen so that Windows and OSX could run under Xen. Of course, if that is so, the windows and OSX will be slow but for testing purposes, it could be useful.
I prefer the "u" in honour as it seems to be missing these days.
I personally have installed and ran generic Windows XP on Xen using the existing Intel chips with VT support. Performance basically sucks right now because Xen currently uses qemu to emulate bios/disk/network/video for these devices so with a lot of disk or network IO you can basically take the machine to its knees because it starts using up 100% cpu to emulate the IO.
This sig will make it clear that ANYONE can use this post for ANY purpose WITHOUT the written consent of the NFL.
I talked to a "Dell Account Manager" at Intel, who informed me that in the Dell Inspiron 9400, VT was switched off using a BIOS switch, but that it could be manually turned on. It will be turned on by default later. This is what he said:
"The processors technically support it, but neither Dell nor intel have activated it yet. We are working to get the ecosystem ready before turning it on. Officially we are saying it will be enabled in 1H'06"
"Good news. Through the BIOS, you can turn VT on with the Inspiron 9400 immediately. Just purchase a Intel Core T2300 cpu or higher."
You're right, nobody ported Xen to NetBSD. That's not how Xen works. What happened was someone ported NetBSD to Xen. Instead of this new version of NetBSD accessing hardware, it asks Xen to do it. This required no modification of Xen, just modification of the NetBSD kernel to avoid accessing hardware directly. It's comparable with porting NetBSD to a new chip architecture.
Xen doens't trap access to real hardware (if a guest tries to access hardware it will get a kernel panic). Instead, Xen presents to the guest OSes fake devices with a custom interface designed to be efficient under Xen. So a Xen guest won't try to access your network adapter or disk controller, it will use the Xen interface to send a descriptor to the virtual device backend driver.
:) runs on: different MMU, different system bus.
Privileged guests (usually the domain0 guest) are an exeption to this because they do have direct access to the real hardware (and the hypervisor doesn't do any work here, privileged domains write *directly* to the device's registers). Privileged domains also runs the virtual device backend drivers, which does the work for virtual devices in the guest OSes.
So unprivileged Xen guests don't think they have access to the real hardware, instead they use virtual devices though custom Xen drivers.
Also, another reason why you need Xen-modified kernels is virtual memory: guest OSes (privileged and non-privileged) don't have direct access to page tables, CR3 register, etc.
When they want to update a page table entry or do a context switch they have to ask the hypervisor to do it; so the VM system needs to be changed to this.
NetBSD on Xen is a port in the NetBSD terminology, the same way NetBSD/mac68k and NetBSD/sun3 are 2 different ports. The machine NetBSD/Xen runs on is different from the machine NetBSD/i386 (which should really be NetBSD/pci386