This section gives you an overview of how the management server organizes the operation of multiple agents within VMware vCenter.
The below distribution algorithm works for both virtual appliances and agents installed in Windows. All agents must be registered on the management server. All agents must be connected to vCenter Server.
Distribution algorithm
The management server evenly distributes the virtual machines between the agents. By evenly, we mean that each agent manages an equal number of machines. The amount of storage space occupied by a virtual machine is not counted.
However, when choosing an agent for a machine, the management server tries to optimize the overall system performance. In particular, the management server considers the agent and the virtual machine location. An agent hosted on the same host is preferred. If there is no agent on the same host, an agent from the same cluster is preferred.
Once a virtual machine is assigned to an agent, all centralized backups of this machine will be delegated to this agent.
Redistribution
Redistribution takes place each time the established balance breaks, or, more precisely, when a load imbalance among the agents reaches 20 percent. This may happen when a machine or an agent is added or removed, or a machine migrates to a different host or cluster, or if you manually bind a machine to an agent. If this happens, the management server redistributes the machines using the same algorithm.
For example, you realize that you need more agents to help with throughput and deploy an additional virtual appliance to the cluster. The management server will assign the most appropriate machines to the new agent and update the centralized backup plans on the involved agents. The old agents' load will reduce.
When you remove an agent from the management server, the machines assigned to the agent are distributed among the remaining agents. However, this will not happen if an agent gets corrupted or is deleted bypassing the management server. Redistribution will start only after you remove such agent from the management server.
Viewing the distribution result
You can view the result of the automatic distribution in the Agent column available for each virtual machine on the management server. Also, it is displayed in the management server options. To access this window, select Options > Management server options from the top menu, and then select Agent for ESX(i) binding.
Manual binding
The Agent for ESX(i) binding option lets you exclude a virtual machine from this distribution process by specifying the agent that must always back up this machine. The management server will continue maintaining the overall balance, but it is allowed to pass the machine to a different agent only if the original agent is removed.
Tips on setup
Below are brief instructions on how to set up some of the available configurations. For detailed information about integration with vCenter see the "VMware vCenter integration" section.
Make sure that all agents are registered on the management server. If you deploy virtual appliances from an OVF template, you need to add them to the management server manually.
In any case you can bind one or more virtual machines to the agents manually.
Do not create local backup plans on agents if you want to make the best of the automatic distribution.