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
