Hi, >First off, please don''t reply to some random thread if you indend >to open a new one. sorry for this, I just was to lasy, I take care not to do it again. OK, I have the following: Two servers connected via NFS to a storage-solution. Both servers have the same hardware and same software (SLES 10.0b3) on it, both are running XEN 3.0.0 and some Linux-guests for testing. I''m able to do "xm save/restore", "xm migrate --live ..." etc. >Then, for failover, I don''t see a reason why you shouldn''t be able to >apply the normal linux failover solutions to xen domUs, like heartbeat OK, but heartbeat just checks if the other machine is still there and then it can do s.th., f.ex. starting the domU that just crashed on the master machine on the backup machine! But it would be better to make in an fixed (and short as possible) interval snapshots of the running VM including processor and memory (like "xm save" does, but without interrupting or even disturbing the VM too much), putting it on the shared storage and if the domU crashes restoring it from the backup host quite fast and in a most actual state! I''ve read several times the XEN 3 should support failover with the live-migration, but how can I use it for the BEFORE the master crashes? >The main problem with failover solutions always is to make sure the >failing host releases its MAC or IP. Solutions include disabling the With XEN 3 and the live-migration this should not be a big problem, or? >failover solutions usually provide means to execute a script whenever >action is needed, so issuing the right commands to your dom0 should be >quite easy. Yes, it should be, but only if you know the right commands and there parameters :-) Thanks for your answers, -- Chau y hasta luego, Thorolf _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi all, where do I find more information about the following: xc_save xcfd iofd domid maxit maxf flags xc_restore xcfd iofd domid nr_pfns store_evtchn console_evtchn What are the commands doing exactly and how are they doing it, what do the parameters mean exactly? Is it possible to realise a failover with this, can xc_save make snap-shots of a currently running VM without disturbing it much so if this host/guest crashes can I restore it quickly with the most actual status? Thanks a lot for your help, -- Chau y hasta luego, Thorolf _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
On Thursday 09 February 2006 11:05, Thorolf Godawa wrote:> Hi all, > > where do I find more information about the following: > > xc_save xcfd iofd domid maxit maxf flags > xc_restore xcfd iofd domid nr_pfns store_evtchn console_evtchn > > What are the commands doing exactly and how are they doing it, what do > the parameters mean exactly? > > Is it possible to realise a failover with this, can xc_save make > snap-shots of a currently running VM without disturbing it much so if > this host/guest crashes can I restore it quickly with the most actual > status?Well, to restore a snapshot, the on-disk and in-memory state has to match, otherwise you''d most likely badly corrupt your filesystem. so you''d have to xm save your domain (stopping it), create a snapshot of all mounted filesystems and swap partitions, and restart the domain. I don''t think that could be done in less than a second, iow, quite disturbing to your primary domU. Next problem would be: if your master domU fails, your memory dump most likely already contains the reason for the failure (runaway process, memory leak, corrupted pointers...) so you don''t gain much with that sort of failover, your secondary domU will most likely fail too in short order. If you use an minimal kernel and tuned startup scripts starting only the absolutely needed services, a fresh reboot of a domU shouldn''t take much more time than a restore from dump would, so for real-world applications that seems to be the better solution. or, run a second domU with the same services in hot-standby, and just switch over the IP and MAC adress in case of failure. /Ernst _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users