Exchange Server Role Requirements Calculator: DAGs required

Occasional Contributor

I have a quick question regarding the “Exchange Server Role Requirements Calculator”.
I have a medium sized Exchange 2010 Environment that I would like to upgrade to Exchange 2016.
The current Exchange 2010 design is based on an Active/Passive design with a Single DAG that is shared across the 7 Mailbox servers. We have around 5500 mailboxes spread across 10 databases.
When I came to put all this detail into the “Exchange Server Role Requirements Calculator” it suggested I have
• 6 Servers in Active site
• 3 Servers in Passive site
I agree with the server design but were a bit surprised when it suggested I have 9 Database Availability Groups? Is this correct? Why can’t I have just one DAG like in my Exchange 2010 environment?


In the attachments:-

  • ExchangeCalc9.1.pdf - Calculator populated with my values
  • ExchangeCalc9.1-Result.pdf - Calculator's recommendation for 9 DAGs

You can force the Calculator to use 1 DAG but then it blows the server configuration

  • ExchangeCalc9.1-WithOneDAG-Result.pdf (Cores and CPU highlighted in RED)




7 Replies

The calculator also assumes you are calculating for 4 copies of DB and you should check the second tab to see the calculation which it did. also the database copy layout tab

Here are the values. I understand that you would have 4x Database Copies per server - That is correct and there are 3 copies of a Database instance replicated - Two on the Primary Datacenter and One on the DR Datacenter.


But where do the 324 copies come from? I know that 9 x 36 = 324 - But that suggests I have 9 DAGs
Surely then the Database Copy Instance Configuration values should be multiplied by 9...?


I still don't get how the Calculator can recommend I use 9 DAGs?


Database Copy Configuration  
Number of Database Copies

/ Server = 4

/ DAG = 36

/ Environment = 324



Database Copy Instance Configuration 
Number of HA Database Copy Instances / DAG

/ Primary Datacenter = 2

/ Secondary Datacenter = 1

 Total = 3


Adding @Vasil Michev and @Tony Redmond @Ross Smith IV to review your calculation

best response confirmed by Andre Schoeman (Occasional Contributor)

Finally, I think I know what the problem is - My SPECINT2006 value was way off - I downloaded this tool "Exchange Processor Query Tool" and it calculated my SPECINT2006 value to be 645. Now the Calculator works correctly and recommends 1 DAG :)

Thanks for sharing your findings. That shows how important is your SPECINT value.


are you hosting it on Physical Machines or on VM Platform?

VMWare Platform

Thank you for helping me get to the bottom if the issue ;)

Just be aware that the current calculator takes no account of the mitigations released for the Meltdown/Spectre vulnerabilities. Some impact is to be expected in most Exchange environments, but you will only be able to confirm the exact effect on performance by running a test load.