As discussed in my previous post, the Exchange 2010 mailbox server which is configured for OAB generation does the group metrics generation as well. This will be enough for small to medium organizations. But, for very large organizations, you may want to configure more mailbox servers to generate group metrics data.
Run the command below to force a server to generate group metrics.
Set-MailboxServer –identity “servername” –ForceGroupMetricsGeneration $true
In the same way, you can disable group metrics generation with the command below.
Set-MailboxServer –identity “servername” –ForceGroupMetricsGeneration $false
An exception to this is the mailbox server responsible for generating the OAB. Even if you explicitly disable group metrics generation using the command above, it will still generate it 
