What is the IBM Notes Traveler Load Balancing algorithm
Tags :Traveler sys admin tips load balancing HA
IBM Lotus Traveler in High Availability mode does a lot of work behind the scenes. It uses Master Monitor servers, load algorithms and server bias to help distribute user device load.
What is the Master Monitor
Each user is assigned a master monitor the first time his/her device connects. The master monitor is essentially the IBM Notes Traveler server responsible for handling any and all work for that user. If the user connects multiple devices, each device will be routed to the master monitor for processing. If no device connects, the master monitor assignment will expire after 24 hours. On each device connection, the IBM Notes Traveler server will decide if the master monitor should be moved, or if no master monitor is currently assigned, which server to assign the user.
Now the load balancing algorithm is actually simple but takes into account the server bias. The server bias is the only part of this that can be adjusted by the administrator. The load balancing is then derived from this bias.
For each request from the device, the local server will determine what is the best server to handle the request. The best server is determined by comparing the AIs of each server. If any bias applies to a server, it is added to the AI. The server with the highest computed AI is chosen. If this server is not currently the master monitor, then it gets assigned as the master monitor for the user and the master monitor bias will apply. To prevent thrashing, a user's master monitor can not be switched again for at least 10 minutes.
IBM has a great example of how bias affects load in the following chart from this InfoLibrary posting
Server 1 (Local Server) Bias = 10%
Server 2 No bias
Server 3 (Master Monitor) Bias = 20%
Load balance winner and master monitor
|Current® AI||AI + Bias||Current AI||AI + Bias||Current AI||AI + Bias|
As you can see, there is a lot of action behind the scenes in IBM Lotus Traveler HA to help distribute load across your Traveler Pool. I hope that helps with some basics to get started..