Re: [Users] two node ovirt cluster with HA

I am adding Tareq for the Power Management implementation. Dafna On 01/27/2014 11:48 AM, Karli Sjöberg wrote: > On Mon, 2014-01-27 at 11:11 +0000, Dafna Ron wrote: >> Powering off the host will never trigger vm migration. >> As far as engine is concerned it just lost connection to the host, but >> has no way of telling if the host is down or if a router is down. > Can´t it at least check with power management if the Host status is down > first? > > I mean, if the network is down there will be no response from either PM > or Host. But if PM is up and can tell you that the Host is down, sounds > rather clear cut to me... > > Seems to me the VM's would be restarted sooner if the flow was altered > to first check with PM if it´s a network or Host issue, and if Host > issue, immediately restart VM's on another Host, instead of waiting for > a potentially problematic Host to boot up eventually. > > /K > >> since vm's can continue running on the host even if engine has no >> access >> to it, starting the vm's on the second host can cause split brain and >> data corruption. >> >> The way that the engine knows what's going on is by sending heath check >> queries to the vdsm. >> Power management will try to reboot a host when the health checks to >> vdsm will not be answered. >> So... if engine gets no reply and has no way of rebooting the host, the >> host status will be changed to Non-Responsive and the vm's will be >> unknown because engine has no way of knowing what's happening with the >> vm's. >> Since reboot of the host will kill the vm's running on it - this will >> never cause any vm migration but... along with the High-Availability vm >> feature, you will be able to have some of the vm's re-started on the >> second host after the host reboot (and that is only if Power Management >> was confirmed as successful). >> >> VM migration is only triggered when: >> 1. Cluster configuration states that the vm should be migrated in case >> of failure >> 2. Engine has access to the host - so the failure is on the storage >> side >> and not the host side. >> 3. the vms are not actively writing (although there might be a new RFE >> for it). >> >> hope this clears things up >> >> Dafna >> >> >> >> On 01/27/2014 10:11 AM, Andrew Lau wrote: >>> Hi, >>> >>> Have you got power management enabled? >>> >>> That's the fencing feature required for the engine to ensure that the >>> host is actually offline. It won't resume any other VMs to prevent >>> potential VM corruption (eg. VM running on multiple hosts). >>> >>> Andrew. >>> >>> On Jan 27, 2014 5:12 PM, "Jaison peter" <urotrip2(a)gmail.com >>> <mailto:urotrip2@gmail.com>> wrote: >>> >>> Hi all , >>> >>> I was setting a two node ovirt cluster with ovirt engine on >>> seperate node . I completed the configuration and tested VM live >>> migrations with out any issues . Then for checking cluster HA I >>> powered down one host and expected vms running on that host to be >>> migrated to the other one . But nothing happened , Engine >>> detected >>> host as un-rechable and marked it as non-operational and vm >>> ran on >>> that host went to 'unknown state' . Is that not possible to setup >>> a fully HA ovirt cluster with two nodes ? or else is that my >>> configuration problem ? please advice . >>> >>> Thanks & Regards >>> >>> Alex >>> >>> _______________________________________________ >>> Users mailing list >>> Users(a)ovirt.org <mailto:Users@ovirt.org> >>> http://lists.ovirt.org/mailman/listinfo/users >>> >>> >>> >>> _______________________________________________ >>> Users mailing list >>> Users(a)ovirt.org >>> http://lists.ovirt.org/mailman/listinfo/users >> >> -- >> Dafna Ron >> _______________________________________________ >> Users mailing list >> Users(a)ovirt.org >> http://lists.ovirt.org/mailman/listinfo/users > >