Hi List, now that I get closer to setup my first productive XEN machine I wonder how a cluster will work with XEN. As I''m very new to cluster at all please help me to understand how things are supposed to work. I expect a cluster work on three layers: Application xx y zzz Cluster ------------------ Hardware HH HH HH HH HH So one Cluster is build by 5 nodes here. Involving XEN - does that mean following a) or b)? a) Application xx y zzz XENdomU UUUUUUU UUUUU XEN dom0 xxxxxxxxxxxxxxxxxx Cluster ------------------ Hardware HH HH HH HH HH So again five node build a cluster hosting ONE xen dom0 with two domU''s b) Application x y Cluster --- --- XENdomU U U U U U XEN dom0 xxxx xxxx xxxx Hardware HH HH HH Here three physical servers host a xen dom0 each with two domU''s. Two of these domU''s on diffrent HH now build a cluster. Tnanx for advise Mat _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
--- Mathias Diehl <md@evoconcept.de> wrote:> now that I get closer to setup my first productive XEN machine I > wonder how a cluster will work with XEN.So did I: http://lists.xensource.com/archives/html/xen-users/2005-03/msg00010.html> So one Cluster is build by 5 nodes here. Involving XEN - does > that mean following a) or b)?(...)> b) > > Application x y > Cluster --- --- > XENdomU U U U U U > XEN dom0 xxxx xxxx xxxx > Hardware HH HH HH > > Here three physical servers host a xen dom0 each with two > domU''s. Two of these domU''s on diffrent HH now build a cluster.The correct answer is b. The Xen hypervisor kernel which runs dom0 and domU must always be right on the hardware. It runs in kernel-level space, not user level. That means nothing can exist between it and the hardware, not even a cluster kernel. So you can''t, for example, create a highly available Xen hypervisor. You can create several Xen hypervisor machines and thus dozens of Xen domUs with which to run your cluster upon (plan B above). You could also create a cluster and use a virtualization product that runs in user space such as VMware ($$), UML (free), or FreeVPS (also free). FreeVPS has the most limitations but should be the fastest of the three. If you can accept the limitations, that''s what I would choose. UML has two modes for running processes, one in which the processes are all visible to the host (tt mode) and one in which all processes are hidden in a seperate kernel space and only one thread is visible to the host (skas). Skas is supposed to be faster but I would think tt mode would lend itself better to SSI clusters such as OpenSSI in which the threads of an app are spread across the cluster. In these clusters a multi-threaded app (such as a tt mode UML machine) performs better than a single-threaded app (such as a skas UML machine). But if you''re leaning more toward high availability and you need UML''s capabilities then perhaps skas would be the way to go. My needs are mostly high-availability with some load balancing. I would buy three VT-enabled servers, install Xen on each, create three domUs and cluster them with OpenSSI. That way I''ve got high availability with reasonably decent load balancing. If I need more horsepower it''s so very easy to scale up; just add another Xen node+domU and add it to the cluster (even mid-day). If I need to do maintenance, the high-availability features take over (even mid-day). Disclaimer: All of my comments could be poppycock, especially the bit about UML''s skas mode. I haven''t tested *any* of it, I just have been reading alot about clustering lately. Hope this helps! CD * Bad news: We''ve all broken God''s 10 Commandments. Lust is adultery (Matt. 5:27-28), hate is murder (1 John 2:9). Break one and you''ve broken them all (James 2:10). We *all* deserve hell. * Good news: Jesus paid my penalty. Turn from your sin & ask God''s forgiveness by His blood -- while you still have time! NeedGod.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> You can create several Xen hypervisor machines and thus dozens > of Xen domUs with which to run your cluster upon (plan B > above).Here''s an OpenSSI doc explaining how to do this: http://www.openssi.org/cgi-bin/view?page=docs2/1.9/debian/xen-howto.txt Again, this is OpenSSI running in domUs on a Xen hypervisor on real hardware. This is *not* Xen running on an OpenSSI kernel running on real hardware. For that you need a user-space virtulization solution. CD * Bad news: We''ve all broken God''s 10 Commandments. Lust is adultery (Matt. 5:27-28), hate is murder (1 John 2:9). Break one and you''ve broken them all (James 2:10). We *all* deserve hell. * Good news: Jesus paid my penalty. Turn from your sin & ask God''s forgiveness by His blood -- while you still have time! NeedGod.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
--- Chris de Vidal <chris@devidal.tv> wrote:>> So one Cluster is build by 5 nodes here. Involving XEN - does >> that mean following a) or b)? >(...) >> b) >> >> Application x y >> Cluster --- --- >> XENdomU U U U U U >> XEN dom0 xxxx xxxx xxxx >> Hardware HH HH HH >> >> Here three physical servers host a xen dom0 each with two >> domU''s. Two of these domU''s on diffrent HH now build a cluster. > > >The correct answer is b.One think I didn''t understand in this option is: why do you need to introduce another software layer (XEN in this case) in the system? It seems to me that the desirable features come from the cluster layer (OpenSSI) not from the XEN layer. Am I correct? Thanks, Reynaldo _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
--- "Novaes, Reynaldo" <reynaldo.novaes@hp.com> wrote:> One think I didn''t understand in this option is: why do you need > to introduce another software layer (XEN in this case) in the > system? It seems to me that the desirable features come from the > cluster layer (OpenSSI) not from the XEN layer. Am I correct?Cluster + virtualization means to me high availability+load balancing with the flexibility of virtualization. In some situations it might be adventageous to make many little virtual machines highly available + load balanced. CD * Bad news: We''ve all broken God''s 10 Commandments. Lust is adultery (Matt. 5:27-28), hate is murder (1 John 2:9). Break one and you''ve broken them all (James 2:10). We *all* deserve hell. * Good news: Jesus paid my penalty. Turn from your sin & ask God''s forgiveness by His blood -- while you still have time! NeedGod.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Greetings! I am very interested in the specifics of this solution. As I understand it you want to run FreeVPS or UML... on OpenSSI running under xen. What advantage would there be to running this in conjunction with xen in your configuration? The problem with running User mode apps on a cluster is that they are improperly threaded for running over a cluster. Other issues that would be encountered would include cache thrashing, latency. I spent over a year trying to get a project together to patch Open Mosix so that it would run an emulator on top of it. Had some smart people working on it that indicated there is no general solution for running non properly threaded applications on top of a cluster...that was nearly 4 years ago so things might have changed. If you could explain this further it would be appreciated. Regards, hikenboot --------------------------------- Yahoo! Photos Got holiday prints? See all the ways to get quality prints in your hands ASAP. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users