Virtual machine binding

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.

Distribution algorithm

The virtual machines are automatically evenly distributed between Agents for VMware. 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 software tries to optimize the overall system performance. In particular, the software 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 backups of this machine are 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. 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 from manually from vSphere. Redistribution will start only after you remove such agent from the web interface.

Viewing the distribution result

You can view the result of the automatic distribution:

  • in the Agent column for each virtual machine on the All devices section
  • in the Assigned virtual machines section of the Details panel when an agent is selected in the Settings > Agents section

Manual binding

The Agent for VMware binding lets you exclude a virtual machine from this distribution process by specifying the agent that must always back up this machine. The overall balance will be maintained, but this particular machine can be passed to a different agent only if the original agent is removed.

To bind a machine with an agent

  1. Select the machine.

  2. Click Details.

    In the Assigned agent section, the software shows the agent that currently manages the selected machine.

  3. Click Change.
  4. Select Manual.
  5. Select the agent to which you want to bind the machine.
  6. Click Save.

To unbind a machine from an agent

  1. Select the machine.

  2. Click Details.

    In the Assigned agent section, the software shows the agent that currently manages the selected machine.

  3. Click Change.
  4. Select Automatic.
  5. Click Save.

Disabling automatic assignment for an agent

You can disable the automatic assignment for Agent for VMware to exclude it from the distribution process by specifying the list of machines that this agent must back up. The overall balance will be maintained between other agents.

Automatic assignment cannot be disabled for an agent if there are no other registered agents, or if automatic assignment is disabled for all other agents.

To disable automatic assignment for an agent

  1. Click Settings > Agents.
  2. Select Agent for VMware for which you want to disable the automatic assignment.
  3. Click Details.
  4. Disable the Automatic assignment switch.

Usage examples

  • Manual binding comes in handy if you want a particular (very large) machine to be backed up by Agent for VMware (Windows) via a fibre channel while other machines are backed up by virtual appliances.
  • Manual binding is necessary if you are using SAN hardware snapshots. Bind Agent for VMware (Windows) for which SAN hardware snapshots are configured with the machines that reside on the SAN datastore.
  • It is necessary to bind VMs to an agent if the agent has a locally attached storage.
  • Disabling the automatic assignment enables you to ensure that a particular machine is predictably backed up on the schedule you specify. The agent that only backs up one VM cannot be busy backing up other VMs when the scheduled time comes.
  • Disabling the automatic assignment is useful if you have multiple ESXi hosts that are separated geographically. If you disable the automatic assignment, and then bind the VMs on each host to the agent running on the same host, you can ensure that the agent will never back up any machines running on the remote ESXi hosts, thus saving network traffic.