This customer uses the Interactive Session Support facility to provide a name servier which returns the least loaded node according to a site defined metric. This allows a user to be given the least loaded operational node when he or she logs in.
This metric is based on the number of logged in users, with some weight given to those using Xstations. Every few minutes, the system is scanned to evaluate the following:
Xterminals*3 + Telnet*2 + Process
Where:
This metric tries to balance users across the system while providing some factor for their likely future utilization. A metric based on the CPU load average is too dependent on the current load to provide good balancing.
The metric can also be set to return a low priority if the file /etc/iss.nologin exists. This allows the administrator to drain the interactive use of a node if there is scheduled system maintenance. When the maintenance is completed, the file can be removed and the metric will return the correct value for the node. Users will therefore see an improved availability, since they will not be given a node that is about to shutdown.