Hi all, I''m going to install Xen on a new 64bit capable machine with 16GB RAM and two quad-core Xeon. The domU''s are (for migration issues) all 32bit PAE PV. My question is, should I install a 32bit PAE (which i prefer) or a 64bit Xen? Are there any known performance issues running 32bit PAE PV''s on a 64bit Xen? It''s really unlikely that the machine will be upgraded to more than 16GB. And btw. does someone know if the 32bit PAE PV domU''s memory limit is also at 16GB or smaller (well, assuming more physical RAM)? Thanks for any suggestions in advance! Greetings -- Stephan Seitz Senior System Administrator *netz-haut* e.K. multimediale kommunikation zweierweg 22 97074 würzburg fon: +49 931 2876247 fax: +49 931 2876248 web: www.netz-haut.de <http://www.netz-haut.de/> registriergericht: amtsgericht würzburg, hra 5054 _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Aug-22 17:20 UTC
Re: [Xen-users] Xen 3.1 64bit / 32bit domU performance
> I''m going to install Xen on a new 64bit capable machine with 16GB RAM and > two quad-core Xeon. The domU''s are (for migration issues) all 32bit PAE PV. > My question is, should I install a 32bit PAE (which i prefer) or a 64bit > Xen? Are there any known performance issues running 32bit PAE PV''s on a > 64bit Xen? It''s really unlikely that the machine will be upgraded to more > than 16GB.AFAIK, 32-bit PAE PV guests should perform well on 64-bit Xen - if anything, they might well be better performing than 64-bit guests. This is because protecting Xen from 64-bit guests incurs a higher performance penalty than for protecting it from 32-bit guests. By the way, I don''t think it''s possible to suspend / resume or live migrate 32-bit PV guests on a 64-bit Xen yet. I guess that''ll be in a future release. Also, I understand that pre-3.1 32-bit kernels won''t run on vanilla 3.1, but subsequent patches that are in the -unstable tree provide compatibility for these older kernel builds too. HVM guests are a separate issue, by the way, as their memory etc is handled differently.> And btw. does someone know if the 32bit PAE PV domU''s memory limit is also > at 16GB or smaller (well, assuming more physical RAM)?I''m not sure on this. Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users