Detecting System Failure

When a system crashes or is powered off, it stops sending heartbeats to other systems in the cluster. By default, other systems in the cluster wait 21 seconds before declaring it dead. The time of 21 seconds derives from 16 seconds default timeout value for LLT peer inactive timeout, plus 5 seconds default value for GAB stable timeout. The default peer inactive timeout is 16 seconds, and can be modified in the /etc/llttab file. For example, to specify 12 seconds:

GAB stable timeout can be changed by specifying:

Though this can be done, we do not recommend changing the values of the LLT peer inactive timeout and GAB stable timeout.

If a system reboots, it becomes unavailable until the reboot is complete. The reboot process kills all processes, including HAD. When the VCS process is killed, other systems in the cluster mark all service groups that can go online on the rebooted system as autodisabled. The AutoDisabled flag is cleared when the system goes offline. As long as the system goes offline within the interval specified in the ShutdownTimeout value, VCS treats this as a system reboot. The ShutdownTimeout default value of 120 can be changed by modifying the attribute. See System Attributes for details.