Hi Everyone, I''ve noticed some VPS hosting companies offering a Xen "HVM" option. What are the advantages of a Linux HVM VPS over a PV one? Many Thanks _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Jonathan, The only big advantage is that customers can install operating systems that do not support pv operation (e.g. Windows). Some small advantages like using own GRUB or kernels can be achieved in pv environment, too (pvgrub, pygrub), but those hosters probably don''t enable that for pv VPS. Another little point is that not all HVM features are available for pv guests, especially with pv_ops guest and host kernels (for example: USB passthrough, PCI / VGA passthrough; the first two not yet with pv_ops kernels, VGA passthrough is always only available for HVMs). But as long as you don''t want to offer physical hardware to your clients, this doesn''t matter for VPS hosting. Probably I missed an important point, but AFAIK there is no advantage of having a Linux server system in a HVM instead of a PV VM. Felix Am 27.08.2010 08:41, schrieb Jonathan Tripathy:> Hi Everyone, > > I''ve noticed some VPS hosting companies offering a Xen "HVM" option. > What are the advantages of a Linux HVM VPS over a PV one? > > Many 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
Hi Felix, This is exactly what I thought. Currently with my VPS offering, I use pygrub, with the user''s kernel being stored on their disk image, so they can change it if they like Cheers ________________________________ From: xen-users-bounces@lists.xensource.com on behalf of Felix Kuperjans Sent: Fri 27/08/2010 11:33 To: xen-users@lists.xensource.com Subject: Re: [Xen-users] Why HVM? Hi Jonathan, The only big advantage is that customers can install operating systems that do not support pv operation (e.g. Windows). Some small advantages like using own GRUB or kernels can be achieved in pv environment, too (pvgrub, pygrub), but those hosters probably don''t enable that for pv VPS. Another little point is that not all HVM features are available for pv guests, especially with pv_ops guest and host kernels (for example: USB passthrough, PCI / VGA passthrough; the first two not yet with pv_ops kernels, VGA passthrough is always only available for HVMs). But as long as you don''t want to offer physical hardware to your clients, this doesn''t matter for VPS hosting. Probably I missed an important point, but AFAIK there is no advantage of having a Linux server system in a HVM instead of a PV VM. Felix Am 27.08.2010 08:41, schrieb Jonathan Tripathy: Hi Everyone, I''ve noticed some VPS hosting companies offering a Xen "HVM" option. What are the advantages of a Linux HVM VPS over a PV one? Many 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
> Hi Jonathan, > > The only big advantage is that customers can install operating systemsthat do> not support pv operation (e.g. Windows). Some small advantages likeusing own> GRUB or kernels can be achieved in pv environment, too (pvgrub,pygrub), but> those hosters probably don''t enable that for pv VPS. > Another little point is that not all HVM features are available for pvguests,> especially with pv_ops guest and host kernels (for example: USBpassthrough,> PCI / VGA passthrough; the first two not yet with pv_ops kernels, VGA > passthrough is always only available for HVMs). But as long as youdon''t want> to offer physical hardware to your clients, this doesn''t matter forVPS> hosting. > > Probably I missed an important point, but AFAIK there is no advantageof> having a Linux server system in a HVM instead of a PV VM. >How good is VNC access under PV these days? With HVM you get a virtual keyboard, video, and mouse which can get you out of trouble if you do something dumb and lose network access. James _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
________________________________ From: xen-users-bounces@lists.xensource.com on behalf of James Harper Sent: Fri 27/08/2010 11:43 To: Felix Kuperjans; xen-users@lists.xensource.com Subject: RE: [Xen-users] Why HVM?> Hi Jonathan, > > The only big advantage is that customers can install operating systemsthat do> not support pv operation (e.g. Windows). Some small advantages likeusing own> GRUB or kernels can be achieved in pv environment, too (pvgrub,pygrub), but> those hosters probably don''t enable that for pv VPS. > Another little point is that not all HVM features are available for pvguests,> especially with pv_ops guest and host kernels (for example: USBpassthrough,> PCI / VGA passthrough; the first two not yet with pv_ops kernels, VGA > passthrough is always only available for HVMs). But as long as youdon''t want> to offer physical hardware to your clients, this doesn''t matter forVPS> hosting. > > Probably I missed an important point, but AFAIK there is no advantageof> having a Linux server system in a HVM instead of a PV VM. >How good is VNC access under PV these days? With HVM you get a virtual keyboard, video, and mouse which can get you out of trouble if you do something dumb and lose network access. James ----------------------------------------------------------------- Hi James, I just use xm console to get access to my linux shell without network access. VNC (for desktop PV environments) works fine if you install a VNC server (however this is network based) Cheers _______________________________________________ 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
I thought there was an pvfb frontent, too, but I''ve never actually used it. For Linux consoles, virtual keyboard / mouse (e.g. for watching kernel messages) is not necessary because the XEN hypervisor console offers all capabilities of usual framebuffers, too. In addition, although quite common nowadays, desktops should not be part of a server system, web-based or remote administration GUIs are usually less resource consuming (on the server), provide more secure access and are easier to access (in case of web administration GUIs). If someone really wants a desktop, it would be much better on Linux not to install a full X server with input and video drivers, but instead using a VNC server which usually is more lightweight (You would access your virtual desktop with VNC anyway, it''s just the question whether Dom0 or DomU is providing the VNC service). Felix Am 27.08.2010 12:45, schrieb Jonathan Tripathy:> > > ------------------------------------------------------------------------ > *From:* xen-users-bounces@lists.xensource.com on behalf of James Harper > *Sent:* Fri 27/08/2010 11:43 > *To:* Felix Kuperjans; xen-users@lists.xensource.com > *Subject:* RE: [Xen-users] Why HVM? > > > Hi Jonathan, > > > > The only big advantage is that customers can install operating systems > that do > > not support pv operation (e.g. Windows). Some small advantages like > using own > > GRUB or kernels can be achieved in pv environment, too (pvgrub, > pygrub), but > > those hosters probably don''t enable that for pv VPS. > > Another little point is that not all HVM features are available for pv > guests, > > especially with pv_ops guest and host kernels (for example: USB > passthrough, > > PCI / VGA passthrough; the first two not yet with pv_ops kernels, VGA > > passthrough is always only available for HVMs). But as long as you > don''t want > > to offer physical hardware to your clients, this doesn''t matter for > VPS > > hosting. > > > > Probably I missed an important point, but AFAIK there is no advantage > of > > having a Linux server system in a HVM instead of a PV VM. > > > > How good is VNC access under PV these days? With HVM you get a virtual > keyboard, video, and mouse which can get you out of trouble if you do > something dumb and lose network access. > > James > > ----------------------------------------------------------------- > > Hi James, > > I just use xm console to get access to my linux shell without network > access. VNC (for desktop PV environments) works fine if you install a > VNC server (however this is network based) > > Cheers > > > > _______________________________________________ > 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_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Fri, Aug 27, 2010 at 08:43:01PM +1000, James Harper wrote:> > Hi Jonathan, > > > > The only big advantage is that customers can install operating systems > that do > > not support pv operation (e.g. Windows). Some small advantages like > using own > > GRUB or kernels can be achieved in pv environment, too (pvgrub, > pygrub), but > > those hosters probably don''t enable that for pv VPS. > > Another little point is that not all HVM features are available for pv > guests, > > especially with pv_ops guest and host kernels (for example: USB > passthrough, > > PCI / VGA passthrough; the first two not yet with pv_ops kernels, VGA > > passthrough is always only available for HVMs). But as long as you > don''t want > > to offer physical hardware to your clients, this doesn''t matter for > VPS > > hosting. > > > > Probably I missed an important point, but AFAIK there is no advantage > of > > having a Linux server system in a HVM instead of a PV VM. > > > > How good is VNC access under PV these days? With HVM you get a virtual > keyboard, video, and mouse which can get you out of trouble if you do > something dumb and lose network access. >PVFB (paravirtual framebuffer) has been available for years for Linux PV guests.. so each guest using pvfb will have a separate qemu-dm providing the VNC access. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hello, Le 27 août 2010 à 08:41, Jonathan Tripathy a écrit :> I''ve noticed some VPS hosting companies offering a Xen "HVM" option. What are the advantages of a Linux HVM VPS over a PV one?I''m working for a hosting company and seriously considering switching to HVM instead of PV. We are using PV x86_64 linux guests for several years (100+ VMs) and I''ve just discovered that PV guest where very bad on some benchmarks involving many process creation (unixbench). The Host : Xeon L5530 (HT disabled) , 24 GB mémory The guest : 4 vCPUS, 20 GB memory. Unixbench : host = 4000, PV guest = 1500, HVM guest = 3900 With modern CPUs (Xeon 5500 and 5600 here) and new PV drivers on the guest (Linux 2.6.36) HVM gives very low overhead and the performances of HVM guests are very closed to PV guests. With HVM you can use Remus and memory sharing. Regards, Frederic. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Aug 31, 2010 at 10:40:28AM +0200, Frédéric VANNIÈRE wrote:> Hello, > > Le 27 août 2010 à 08:41, Jonathan Tripathy a écrit : > > I''ve noticed some VPS hosting companies offering a Xen "HVM" option. What are the advantages of a Linux HVM VPS over a PV one? > > I''m working for a hosting company and seriously considering switching to HVM instead of PV. > > We are using PV x86_64 linux guests for several years (100+ VMs) and I''ve just discovered that PV guest where very bad on some benchmarks involving many process creation (unixbench). > > The Host : Xeon L5530 (HT disabled) , 24 GB mémory > The guest : 4 vCPUS, 20 GB memory. > > Unixbench : host = 4000, PV guest = 1500, HVM guest = 3900 > > > With modern CPUs (Xeon 5500 and 5600 here) and new PV drivers on the guest (Linux 2.6.36) HVM gives very low overhead and the performances of HVM guests are very closed to PV guests. >Yeah, 64bit PV guests have some overhead, and HVM might be faster there (when using PV-on-HVM drivers). 32bit PV guests are fast thought. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users