I want to understand the limitations I will encounter when installing Xen on a 64bit server that does *not* have VT-x capable CPUs. The server is a Dell 2850 (2 dual core 64Bit CPUs; 8 Gb ram; 280Gb raid5, dual 1Gb ethernet ports). This is an older equipment and I have verified that the CPUs do *not* have VT-x. So para-virtualization is mandatory. My understanding of para-virtualization is that whichever distro I choose for dom0, I am thereafter limited in the variety of domU''s I can install. For example if I use Centos 5.7 for the dom0, I can not use Solaris as a domU because of kernel compatibility differences. But could I use other versions of Linux as a domU, such as a recent Fedora? How similar do the kernels have to be when using para-virtualization? More questions: 1) If I use a 64bit Linux distribution for dom0, does the lack of VT-x capability in the CPUs limit me to 32bit domU installations of the same distro? 2) If I must use 32bit domU installs, uniformity might favor a 32bit Dom0. Would a 64bit dom0 running 32bit domU''s pose any special problems in comparison to a 32bit dom0 running the same 32bit domU installs? 3) When a pre-built kernel is listed in a Linux repository as a "xen" kernel, does that mean it can server equally well for dom0 installs as for domU installs? Please comment on how you would proceed with a Xen configuration on a 64bit server without VT-x capability. Thank you in advance for your help. Russ _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Tue, Nov 29, 2011 at 8:11 PM, Russ Brewer <usna78@gmail.com> wrote:> My understanding of para-virtualization is that whichever distro I choose > for dom0, I am thereafter limited in the variety of domU''s I can install.correct> > For example if I use Centos 5.7 for the dom0, I can not use Solaris as a > domU because of kernel compatibility differences.Not exactly. opensolaris (and derivaties/successor, including solaris 11) supports running as PV domU. The kernel is on /platform/i86xpv/ instead of the usual /platform/i86pc You might need newer version of xen though (can''t remember the exact version required), and possibly putting kernel/initrd in dom0 instead of using pygrub.> But could I use other > versions of Linux as a domU, such as a recent Fedora? How similar do the > kernels have to be when using para-virtualization?As long as domU''s kernel can run as PV domU, they should work regardless of version.> > More questions: > 1) If I use a 64bit Linux distribution for dom0, does the lack of VT-x > capability in the CPUs limit me to 32bit domU installations of the same > distro?64 dom0 (or to be accurate, 64bit hypervisor) can run both 32 and 64bit domU> > 2) If I must use 32bit domU installs, uniformity might favor a 32bit Dom0. > Would a 64bit dom0 running 32bit domU''s pose any special problems in > comparison to a 32bit dom0 running the same 32bit domU installs?Nope. In fact, you should always use 64bit hypervisor whenever possible. The dom0 and domU can be 32bit on 64bit, as long as the hypervisor is 64bit. Most distros only supply 64bit hypervisor in 64bit distro version (and thus, 64bit dom0) though.> > 3) When a pre-built kernel is listed in a Linux repository as a "xen" > kernel, does that mean it can server equally well for dom0 installs as for > domU installs?Should be. -- Fajar
Fajar, Thank you very much for those answers and clarifications! Russ On Tue, Nov 29, 2011 at 8:34 AM, Fajar A. Nugraha <list@fajar.net> wrote:> On Tue, Nov 29, 2011 at 8:11 PM, Russ Brewer <usna78@gmail.com> wrote: > > My understanding of para-virtualization is that whichever distro I > choose > > for dom0, I am thereafter limited in the variety of domU''s I can install. > > correct > > > > > For example if I use Centos 5.7 for the dom0, I can not use Solaris as a > > domU because of kernel compatibility differences. > > Not exactly. > > opensolaris (and derivaties/successor, including solaris 11) supports > running as PV domU. The kernel is on /platform/i86xpv/ instead of the > usual /platform/i86pc You might need newer version of xen though > (can''t remember the exact version required), and possibly putting > kernel/initrd in dom0 instead of using pygrub. > > > But could I use other > > versions of Linux as a domU, such as a recent Fedora? How similar do the > > kernels have to be when using para-virtualization? > > As long as domU''s kernel can run as PV domU, they should work > regardless of version. > > > > > More questions: > > 1) If I use a 64bit Linux distribution for dom0, does the lack of VT-x > > capability in the CPUs limit me to 32bit domU installations of the same > > distro? > > 64 dom0 (or to be accurate, 64bit hypervisor) can run both 32 and 64bit > domU > > > > > 2) If I must use 32bit domU installs, uniformity might favor a 32bit > Dom0. > > Would a 64bit dom0 running 32bit domU''s pose any special problems in > > comparison to a 32bit dom0 running the same 32bit domU installs? > > Nope. In fact, you should always use 64bit hypervisor whenever possible. > > The dom0 and domU can be 32bit on 64bit, as long as the hypervisor is > 64bit. Most distros only supply 64bit hypervisor in 64bit distro > version (and thus, 64bit dom0) though. > > > > > 3) When a pre-built kernel is listed in a Linux repository as a "xen" > > kernel, does that mean it can server equally well for dom0 installs as > for > > domU installs? > > Should be. > > -- > Fajar >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users