Historically, NetEye Clusters were configured with DRBD as Master/Slave resources. This led to the following rather cumbersome resource configuration for an N-node cluster:
Note: $SERVICE serves as a placeholder for any Cluster Service running in NetEye 4.
At least ten constraints were necessary to model the required relations (on promote once, collocation 5 times, and after 4 times):
DRBD 9 introduced a nice little convenience feature called “autopromote”. This automatically promotes a node to primary as soon as the DRBD resources’ block device is mounted. If dual primary mode is configured, then this works on up to 2 nodes, otherwise the mount just fails.
We can rely on this behavior to dispose of the ugly Master/Slave part of the above Cluster configuration. The resources can then be reduced to the following:
The constraints also become a lot simpler:
Well, you can’t put Master/Slave resources in a Resource Group. However, as you may have noticed, we just got rid of all master/slave resources. This means we actually can get rid of all constraints! Resource groups already enforce the necessary collocation and order constraints on their members.
The final result is the following 4 Resources ( 1 Group + 3 Members ) per Service/DRBD Device: