On 13 February 2010 14:01, Rafael Micó Miranda <rmicmirregs@xxxxxxxxx> wrote: > Hi Martin, > > Al your questions point to an advanced configuration using Failover > Domains and Service propierties. > > El sáb, 13-02-2010 a las 06:14 +0000, Martin Waite escribió: >> Hi, >> >> Suppose I have 3 services running on 5 nodes. Each node can run only 1 service, 2 nodes are reserved for failover. > > Lets name the services S1, S2, S3, and the nodes N1, N2, N3 and N4, N5 > for the failover ones. > >> >> It is easy to configure rgmanager to cope with the first service node failure by including the 2 failover nodes in the failover domain for each service. > > Yes, you can configure it in the following way (name the failover > domains F1, F2, F3) > > F1: service S1, nodes N1, N4, N5 > F2: service S2, nodes N2, N4, N5 > F3: service S3, nodes N3, N4, N5 > > You'll need to set the failover domains with the properties "restricted" > and "ordered" for this. There is another property, "auto_failback", that > will be of your interest. Keep it in mind. > >> >> However, is it possible to configure rgmanager such that on a second failure, only the failover node that is not currently running a service is considered for use ? > > Yes. Services have the "run exclusive" option. That property will only > allow a service to be run on a node that has no running services. With > this option on, if N1 fails it will fail over the N4. After that if N2 > fails the service S2 will be migrated to N5, and not to N4. > >> >> Further, that if a third failure occurs, the affected service is not migrated at all ? > > Yes. If you have set the "run exclusive" option on the three services > the service will not be migrated to any node according to: > > http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/Cluster_Administration/s1-add-service-CA.html > > >> >> Also, is it possible to rank the services such that if the failover nodes are occupied by low ranking services and the node running a higher ranking service fails, that the lowest ranking service is evicted so that the higher ranking service can be failed over ? >> > > As far as I know, there is no direct function to do what you ask. > > You can play with all this options to get something similar to what you > need. For example I propose you this configuration: > > Nodes: > > N1, N2, N3: service nodes > N4, N5: failover nodes > > Services: > > S1: high ranking service. "Run exclusive" on. > S2, S3: low ranking services. "Run exclusive" off. > > Fail Over Domains: > > F1: service S1. Nodes N1, N4, N5. "Restricted" on. "Ordered on". > "Auto_failback" off. > F2: service S2. Nodes N2, N5, N4. "Restricted" on. "Ordered on". > "Auto_failback" on. > F3: service S3. Nodes N3, N5, N4. "Restricted" on. "Ordered on". > "Auto_failback" on. > > With this configuration you only penalise services S2 and S3 in case of > N2 and N3 failure because both services will run on the same node, but > you keep N4 free for your hing ranking S1 service. With "Auto_failback" > on on faiolver domains F2 and F3 you will automatically migrate S2 or S3 > back to its preferred node when they come back alive, so penalisation > will be shorter in time. > > > Remember that you are talking about a failure of up to 3 nodes in a > cluster of 5 members. Maybe there is no sense in this because depending > on the configuration given you can even lose Quorum before achieving > this situation. > > >> regards, >> Martin >> >> >> -- >> Linux-cluster mailing list >> Linux-cluster@xxxxxxxxxx >> https://www.redhat.com/mailman/listinfo/linux-cluster > > Cheers, > > Rafael > > -- > Rafael Micó Miranda > > -- > Linux-cluster mailing list > Linux-cluster@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/linux-cluster Hi Rafael, Thank you very much for the information. The "run exclusive" option does appear to do what I need. As for the service ranking and eviction scenario - you are correct that this only becomes necessary in the event of multiple failures, and perhaps I don't need to go that far. The easiest solution is to increase the "M" in the "N+M" set of nodes: I can survive one failure where M=1, two where M=2, etc. If more nodes fail than can be failed over, you are entering DR territory. regards, Martin
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