On Nov 27, 2007, at 12:35 PM, Aaron Kulkis wrote:
Frank Bonnet wrote:
Hello Is there some "cluster solutions" with opensuse ? any infos, links welcome
Clustering just makes use of the normally unused "a" "b" and "c" runlevels.
a "heartbeat" program is used to monitor the other cluster members, and then used to take appropriate action to start up or shut down processes in response to which other host(s) in the cluster are up or down.
newer versions of heartbeat will also recover individual services on an otherwise healthy node. it also comes with a sophisticated policy engine so that you can define the order services need to start in, their preferred locations and which services must/must not run together.
man init
to read about run levels a b and c.
More sophisticated clustering software basically just implements a state machine. for example, if you have a three-host cluster, then the valid states are:
Host3 Host2 Host1 Cluster-state down down up 1 down up down 2 up down up 3 down up up 12 up up down 23 up down up 13 up up up 123
In configuring each host, you just determine, for each of the above states, what processes should be running on each host (for example, if host 2 is down, some of the programs that host 2 hormally runs should be started on host 1, some maybe on host 3, and a remainder (or none) are just unavailable until host 2 is back up.
The whole idea is VERY similar to the runlevel concept, except that you can (should) have a lot more states available, depending on the software.
For a two-host cluster, you can completely implement the cluster with runlevels a, b, and c.
Run level a for normal cluster operations. Run level b for when the other host is down. Run level c for deliberately leaving the cluster.
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