This option is effective when backing up virtual machines with Agent for VMware vSphere ESX(i) or Agent for Hyper-V.
This option defines how many virtual machines an agent can back up simultaneously when executing the given backup plan.
The preset is: 2.
If, according to the backup plan, an agent has to start backing up multiple machines at once, it will choose two machines. (To optimize the backup performance, the agent tries to match machines stored on different storages.) Once any of the two backups is completed, the agent chooses the third machine and so on.
You can change the number of virtual machines for an agent to simultaneously back up. The maximum value is 10.
To prohibit simultaneous backup, clear the Back up virtual machines simultaneously check box. The backups will be queued by the agents.
Tips on usage
This option helps you fit more backups in a narrow backup window. However, the intensively working Agent for ESX(i) (Virtual Appliance) increases its host's load. This may slow down the backups and affect the production servers' performance. If the backup speed is still insufficient, consider installing Agent for ESX(i) (Windows) on a separate physical machine. The agent can share the load with the virtual appliances or undertake backup of all the machines.
Remember that you can make a different setting for each agent, depending on its host load, available transports (LAN, SAN, Hot-add) and other factors. To do so, connect the console to the agent and select Options > Default backup and recovery options > Simultaneous VM backup. These settings will be used unless you override them with the common setting set in the backup plan.