We''re looking to buy a new servers. We''re planning on using Xen to consolidate our many boxes into one. Which platform would be the best for this? I''ve searched for documentation supporting either side, but have found none. I have heavily researched the Performance and specs of the processors and platforms. From what I gather Intel is probably going to be my first choice. What are issues that you guys have run into using Xen on either an Intel or AMD with hardware supported virtualization. Has anyone found documents clearly stating which is superior? I am also interested in people''s personal experience with platforms with hardware virtualization enabled. Does Debian Sarge support Xen with VT or SVM? so many question so little time. Thanks. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Matt Ouellette > Sent: 25 July 2006 17:55 > To: xen-users@lists.xensource.com > Subject: [Xen-users] Intel VT platform vs SVM (Pacifica) > > > We''re looking to buy a new servers. We''re planning on using Xen to > consolidate our many boxes into one. Which platform would be the best > for this? > > I''ve searched for documentation supporting either side, but have found > none. I have heavily researched the Performance and specs of the > processors and platforms. From what I gather Intel is > probably going to > be my first choice.I''d like to know why you don''t choose AMD... ;-)> > What are issues that you guys have run into using Xen on > either an Intel > or AMD with hardware supported virtualization. Has anyone found > documents clearly stating which is superior? > I am also interested in people''s personal experience with > platforms with > hardware virtualization enabled.One current problem with VT is the fact that it doesn''t support real-mode in virtualized mode - they have to suse tricks in VM86 mode, which is not nice... AMD processors can run in "Paged Real-mode" in VM86 mode. However, be balanced, real-mode is almost certainly only needed for booting the system, so it''s not a BIG deal. There''s work to use QEMU for the entire real-mode boot process on VT, since that will allow emulating the parts where it''s getting into troubel right now [graphical boot in SuSE for example - the boot-loader uses "clever tricks" to load data into memory above 1MB, and that''s failing in the current VT implementation]. I would think that anything stating that one is clearly superior to the other would be hard to find for a few reasons: 1. The implementation, although done by two differnet companies, are pretty identical [clue might be in the fact that they both closely looked at the VM technology by IBM that just ran out of patent...]. Since the way that the virtualization works is pretty much identical, one can presume that the results of any benchmarking effort would be pretty close too. 2. The AMD processors haven''t been on the market for that long... 3. The by far most time-consuming part of any fully virtualized guest is time spent in emulated devices. For example, a disk-read would incur 5-6 vmexits to write the commands to the IDE controller, then a further interrupt-injection back to the guest to indicate that the data is availble, and finally another vmexit for the read of the data (unless the driver is braindead and does 256 or 512 read operations). Each one of these vmexits cause a full context switch from the guest to the Dom0 application of qemu-dm, and back again. The amount of time spent here is much bigger than any difference between AMD and Intel''s implementations will show - if it takes 500 cycles to do a vmexit on AMD and 550 on Intel, you will not notice when it takes 10000 cycles to performe the rest of the operations, right? [I have a vague idea of how many cycles AMD and Intel take to do a VMEXIT, and no idea whatsoever what the cycles needed for a full context switch, but the order of magnitude of those numbers are probably not completely wrong].> > Does Debian Sarge support Xen with VT or SVM?Xen 3.0.2 supports both VT and SVM - I wouldn''t recommend running anything much older than that, because there''s been a few problems with running HVM in the earlier releases. I hope this helps... -- Mats> > so many question so little time. Thanks. > > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users > > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Matt Ouellette wrote:> We''re looking to buy a new servers. We''re planning on using Xen to > consolidate our many boxes into one. Which platform would be the best > for this? > > I''ve searched for documentation supporting either side, but have found > none. I have heavily researched the Performance and specs of the > processors and platforms. From what I gather Intel is probably going to > be my first choice. > > What are issues that you guys have run into using Xen on either an Intel > or AMD with hardware supported virtualization. Has anyone found > documents clearly stating which is superior? > I am also interested in people''s personal experience with platforms with > hardware virtualization enabled. >I did a little comparison between the two architectures some while ago: http://project-xen.web.cern.ch/project-xen/xen/hardware.html -- Havard _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Haavard Bjerke wrote:> Matt Ouellette wrote: >> We''re looking to buy a new servers. We''re planning on using Xen to >> consolidate our many boxes into one. Which platform would be the best >> for this?>> What are issues that you guys have run into using Xen on either an Intel >> or AMD with hardware supported virtualization. Has anyone found >> documents clearly stating which is superior?> I did a little comparison between the two architectures some while ago: > > http://project-xen.web.cern.ch/project-xen/xen/hardware.htmlI get a 403 forbidden error when attempting to access that page, so you might want to look into that :-) Cheers Andrew _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 7/25/06, Matt Ouellette <mfo62786@thecsl.org> wrote:> [...] > Does Debian Sarge support Xen with VT or SVM?Do you mean binary packages? Or when build from sources? For binaries, I guess that the xen packages from etch and unstable, which contain also hvm support, should be in sarge backports soon, if not already.>From sources it shouldn''t be a problem.Henning _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Henning Sprang wrote:> On 7/25/06, Matt Ouellette <mfo62786@thecsl.org> wrote: >> [...] >> Does Debian Sarge support Xen with VT or SVM? > > Do you mean binary packages? Or when build from sources? For binaries, > I guess that the xen packages from etch and unstable, which contain > also hvm support, should be in sarge backports soon, if not already. >> From sources it shouldn''t be a problem. > > Henning > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-usersI was just wondering if anyone had run into any issues specific to Debian Sarge working with VT or SVM. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of > Matt Ouellette > Sent: 27 July 2006 21:09 > To: Henning Sprang > Cc: xen-users@lists.xensource.com > Subject: Re: [Xen-users] Intel VT platform vs SVM (Pacifica) > > Henning Sprang wrote: > > On 7/25/06, Matt Ouellette <mfo62786@thecsl.org> wrote: > >> [...] > >> Does Debian Sarge support Xen with VT or SVM? > > > > Do you mean binary packages? Or when build from sources? > For binaries, > > I guess that the xen packages from etch and unstable, which contain > > also hvm support, should be in sarge backports soon, if not already. > >> From sources it shouldn''t be a problem. > > > > Henning > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users > I was just wondering if anyone had run into any issues specific to > Debian Sarge working with VT or SVM.I don''t see why there would be any specific issues with this, it''s a pretty autonomous system (the code to support HVM (VT+SVM) is almost all in xen.gz, the hypervisor itself, a small portion is in libxc to deal with setting up the guest memory [calling into the hypervisor] and loading the initial boot-code [hvmloader] into this memory). If you get Xen working on the machine, VT/SVM should work as well (assuming hardware is capable and enabled).>From what I''ve read, quite a few people use Debian Sarge for their Xenplatforms, so I doubt there''s any common problems with it... -- Mats _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Gregory P. Smith
2006-Jul-30 03:43 UTC
Re: [Xen-users] Intel VT platform vs SVM (Pacifica)
On the Pacifica (SVM) or Vanderpool (VT) front... VMware has done research into the actual practical effects of using it performance wise on different workloads: see the message from ksc at the bottom of this thread: http://www.vmware.com/community/message.jspa?messageID=432916 for Xen its important because it allows non xen-targeted guests to run. But don''t expect it to magically enhance performance over not having it. Neither SVM or VT go far enough in what they support in hw to always be a performance win (i believe its page table related?). _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users