KEMP LoadMaster - Scheduling/Balancing Methods

There are various methods of distributing traffic among a cluster or group of servers. The traffic distribution is based on a load balancing algorithm or scheduling method. The schedules are applied on a per Virtual Service basis.

Here is a list of the methods:

Round robin - This method tells the LoadMaster to direct requests to Real Servers in a round robin order.


Weighted round robin - This method allows each server to be assigned a weight to adjust the round robin order. E.g. "Server 1" can get 2 times the request that "Server 2" gets.


Least connection - This method tells the LoadMaster to look at the connections going to each server and send the next connection to the server with the least amount of connections.


Weighted least connection - This method allows each server to be assigned a weight to adjust the least connection order. E.g. "Server 1" can get 2 times the connections that "Server 2" gets.


Agent-Based Adaptive Balancing - This method is resource based load balancing where an agent gets installed on the server and monitors the servers resources (e.g. RAM, CPU...) and then reports back a percentage to the LoadMaster which is used for load balancing. 


Fixed weighting - This method is used for Redundancy rather than Load Balancing, all connections will go to the server with the highest weight in the event this server fails then the server with the next highest weight takes over. 


Weighted response time - This method looks at the response times of the real servers (based on the response time of the server health check) and which every real server is responding fastest gets the next request.


Source IP hash - This method looks at the source IP address that sent the request to the LoadMaster and will create a HASH value for it and if the HASH value is different then it gets sent to a different Real Server.

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Allen Steckling

Round robin, appears to operate per connection, instead of per request. Which for some, is misleading - as hitting refresh on a page, will not bounce you from server to server.

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Andres Garcia de Alba

Hello Allen,

Yes you are correct. Round Robin is based on TCP connections, not the requests that are within the connection. In most cases, refreshing the page on your browser will issue the request within the same open TCP connection; no new connection will be opened.

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service

Meanwhile there are more methods, e.g., resource based (SDN) and resource based (adaptive). What does that mean?

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Andres Garcia de Alba
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license

Hi
I've made a HA setup with 2 windows print servers (Direct return etc. following the guide https://support.kemptechnologies.com/hc/en-us/community/posts/203633333-Load-Balancing-Microsoft-Print-Server).
My setup is made as primary / backup with Scheduling Method as "Fixed Weighting" (Active server with weight 1000 and passive with 500).
The print works fine on the primary, and when taking down the primary down, the backup server takes over.
But, when the primary comes backup, the print continues to be forwarded to the backup server, if i disables the backup server the print is send to primary, but reenabling the backup server will then send the print to the backup server again.
I've disabled persistence, but stil same problem.
After a reboot of the backup server, the print is send to the primary.

Any idea how to get this HA function to work fully automatically?

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Nick Smylie

Hi @license,

This sounds like a persistence issues honestly. It can be hard to say without troubleshooting it. I can open up a support ticket for you and someone from our support team can assist better that way. Please look for our emails.