Already told you. If you are running two-node, make sure your fencing works and you have reliable connectivity between nodes.
if that isn't good enough, add a third node. On 12/1/12 8:58 AM, Hermes Flying wrote: > Actually each Tomcat uses a back-end database that has the notion of > "primary/backup". > I am trying to figure out if by using Pacemaker facilities I can avoid > splitbrain in the database as well. So far from what you described I > seem to get away with it meaning that by fencing, linux-1 will stop so > the secondary database in lunux-2 will become primary. > Am I on the right track here? If you have any recommendations for my > setup (2 linux running: 2 LB/2Tomcat/2Databases) please let me know! > Thank you for your time! > > > ------------------------------------------------------------------------ > *From:* David Coulson <[email protected]> > *To:* Hermes Flying <[email protected]> > *Cc:* General Linux-HA mailing list <[email protected]>; > Digimer <[email protected]> > *Sent:* Saturday, December 1, 2012 3:53 PM > *Subject:* Re: [Linux-HA] Some help on understanding how HA issues are > addressed by pacemaker > > > On 12/1/12 8:48 AM, Hermes Flying wrote: >> Great help! Please allow me to trouble you with one last question. >> >> If I get this, when I use fencing and the corosync fails then linux-2 >> will attempt to crash linux-1 and take over. At this point though >> linux-1 won't try to do anything right? Since it knows it is the >> primary, I mean. > > linux-1 will be powered off or crashed, so i think that speaks for itself. >> >> Then you say:"Any resource previously running on linux-1 will be >> started on linux-2." >> Now at this point: By resource you mean only pacemaker and its >> related modules, right? Because I want Tomcat to be up and running >> and receiving requests in Linux-2 as well, which will be forwarded by >> load balancer of linux-1. Is this correct? > > I mean 'resources managed by pacemaker'. So if you VIP was running on > linux-1, and it fails, and linux-2 fences it, the only place the VIP > can run is linux-2. linux-1 is totally down. >> >> Also in your setup of 2 NICs or 2 switches I assume that the idea is >> that the probability of split-brain due to network failure is very >> low right? Because I have read that it is not possible to avoid >> split-brain without adding a third node. But I may be >> misunderstanding this > A third node will eliminate split brain by definition, as quorum will > only be obtained if a minimum of two nodes are available. > > If you have a diverse network configuration and good change > management, you're probably not going to experience a split brain > unless you have a substantial environment failure that will probably > impact your client ability to access anything. Since you are not > running shared storage, you're not going to experience data loss which > is typically the biggest concern with split brain. > > > _______________________________________________ Linux-HA mailing list [email protected] http://lists.linux-ha.org/mailman/listinfo/linux-ha See also: http://linux-ha.org/ReportingProblems
