Hi List, because I''m still quite new to Linux please kindly advise about hardware. I need a new server and need to understand how xen will handle 32 / 64 bit systems. Main contraint is a 32 software to be running on a domU. So - do I still need to run XEN on a 32bit system or will my software (java application) also run on a 64bit system?. I noticed that I will not be able to run a 32 domU on a 64 dom0 any help would be appreciated. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Might be useful to make a FAQ item for this. On 11/26/05, Mathias Diehl <md@evoconcept.de> wrote:> Hi List, > > because I''m still quite new to Linux please kindly advise about hardware. > > I need a new server and need to understand how xen will handle 32 / 64 bit systems.With Xen you can either have 32bit kernels or 64 bit kernels, not both. If the Dom0 kernel is 64 bit, then xend needs 64bit python to talk to the 64 bit xen hypervisor. 64bit kernel can otherwise run either mixed, 32, or 64 bit userland.> Main contraint is a 32 software to be running on a domU. > > So - do I still need to run XEN on a 32bit system or will my software (java application) also run on a 64bit system?. I noticed that I will not be able to run a 32 domU on a 64 dom0 >64 bit will give you a definite bonus in performance. I''ve seen two times speed jump in some tests for full 64 bit. Even 32bit userland gets a big boost from the extra registers with a 64bit kernel. I''d suggest running a 64bit domU kernel with a 32 bit userland. -- Nicholas Lee http://stateless.geek.nz gpg 8072 4F86 EDCD 4FC1 18EF 5BDD 07B0 9597 6D58 D70C _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Nicholas Lee wrote:> 64 bit will give you a definite bonus in performance. I''ve seen two > times speed jump in some tests for full 64 bit. Even 32bit userland > gets a big boost from the extra registers with a 64bit kernel. > > I''d suggest running a 64bit domU kernel with a 32 bit userland.Does anyone have experience on switching the kernel from 32 to 64 bit without updating any apps. I''m looking to get Xen up and running but that would mean that i have to manually compile 64 bit version and tie that in to the selected distro, while 32 bit versions of Xen are easily available. I''m hoping to start with 32 bit version, and upgrade to 64 bit later on when it is better integrated, by upgrading to 64 bit Dom0 and switching the DomU kernels from 32 bit to 64 bit and dealing with the userland later on. Any hope here? - - S -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFDiGjpqbb3MLg9dhwRAmH1AKCK06yRtrLFIoRBgIZWwEtidKXDrQCgukxM KZllNtXdXYdCDY+FAOF/v7g=ZXzW -----END PGP SIGNATURE----- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 11/27/05, Sami Haahtinen <ressu@ressukka.net> wrote:> I''m hoping to start with 32 bit version, and upgrade to 64 bit later on > when it is better integrated, by upgrading to 64 bit Dom0 and switching > the DomU kernels from 32 bit to 64 bit and dealing with the userland > later on.Switching domU is obviously easy enough. Switching dom0 and xen.gz are both going to be difficult. I''d recommend against it. Problem is you have to upgrade both the userland and kernel at the same time, as xend needs to be 64bit. Its probably possible to: i) upgrade xen.gz and dom0 kernel to 64bit, turn off xend. Would have to cross compile. ii) Create a chroot, and install new 64bit userland into that iii) Reboot with new chroot as root iv) Check everything and start xend. Mistakes are likely to happen at many places, and the above is specific for Debian. Not sure about other distributions. I decided against it myself. -- Nicholas Lee http://stateless.geek.nz gpg 8072 4F86 EDCD 4FC1 18EF 5BDD 07B0 9597 6D58 D70C _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Nicholas Lee wrote:> On 11/27/05, Sami Haahtinen <ressu@ressukka.net> wrote: > >>I''m hoping to start with 32 bit version, and upgrade to 64 bit later on >>when it is better integrated, by upgrading to 64 bit Dom0 and switching >>the DomU kernels from 32 bit to 64 bit and dealing with the userland >>later on. > > Switching domU is obviously easy enough. Switching dom0 and xen.gz > are both going to be difficult. I''d recommend against it.Well, domU is enough for me. I don''t want to bring down all virtualhosts for re-installation...> Problem is you have to upgrade both the userland and kernel at the > same time, as xend needs to be 64bit. Its probably possible to: > .... > Mistakes are likely to happen at many places, and the above is > specific for Debian. Not sure about other distributions. I decided > against it myself.I was thinking more in the line of: 1) backup dom0 2) reinstall dom0 3) clone xen config and fix it to match the new environment it has risks too, but it should take less time than to fiddle with the existing installation and try to force it to 64 bit. My biggest concern was that if i start creating 32 bit domUs, I''m either stuck with 32 bit environment or have to upgrade everything at once. I don''t really like either of those options. But i think i''ll run with 32 bit and upgrade later. - S _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 11/27/05, Sami Haahtinen <ressu@ressukka.net> wrote:> I was thinking more in the line of: > 1) backup dom0 > 2) reinstall dom0 > 3) clone xen config and fix it to match the new environmentSure if you can do it locally, then its no problem. Backup your config, and do a reinstall of dom0.> My biggest concern was that if i start creating 32 bit domUs, I''m eitherYou should be able to replace the 32 bit kernel with the 64 bit kernel without problem. In fact I''m planning to run a mix of 32bit and 64bit userlands. All with 64 bit domU kernels. -- Nicholas Lee http://stateless.geek.nz gpg 8072 4F86 EDCD 4FC1 18EF 5BDD 07B0 9597 6D58 D70C _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Sami Haahtinen <ressu@ressukka.net> writes:> > Any hope here?Normally it works (haven''t tried it in Xen but many times with native kernels) The biggest exceptions are iptables and ipsec (freeswan etc.) which have too broken interfaces to be emulated properly. So you will likely need a 64bit iptables in dom0 at least. I believe the Xen interfaces are also not emulated so in dom 0 you will also need matching tools. This normally means a 64bit python. Doesn''t affect domUs of course. -Andi _______________________________________________ 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 Andi Kleen > Sent: 27 November 2005 03:55 > To: Sami Haahtinen > Cc: xen-users@lists.xensource.com > Subject: [Xen-users] Re: 32 bit versus 64 bit > > Sami Haahtinen <ressu@ressukka.net> writes: > > > > Any hope here? > > Normally it works (haven''t tried it in Xen but many times > with native kernels) > > The biggest exceptions are iptables and ipsec (freeswan etc.) > which have too broken interfaces to be emulated properly. So > you will likely need a 64bit iptables in dom0 at least. > > I believe the Xen interfaces are also not emulated so in dom > 0 you will also need matching tools. This normally means a > 64bit python. > Doesn''t affect domUs of course. > > -Andi >This comment isn''t exactly to Andi''s comments, just general: If you''re planning on running Xen with para-virtualized DomU, that is without AMD SVM [aka Pacifica] or Intel VT, then your DomU needs to be the same bitness (and PAE-setting) as the Dom0 and Xen kernel. So you can''t just mix''n''match DomU''s and Dom0/Xen. With SVM/VT it would be possible to mix any in DomU with a Dom0 that is "bigger" than the DomU. -- Mats _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users