Exchange 2010

Creating a D.A.G (Database Availability Group)

 

A little introduction

The HA functions in Exchange have been changed a little bit; LCR, CCR, SCC and SCR are now away and replaced by D.A.G.

I think it’s a very cool and great feature with Exchange 2010, maybe the best J it makes it able to create a copy of the database to a different server(s). You are able to have more than one copy of it, so your server1 holds an active copy of DB1, server2 and server3 can hold this database as passive if server1 is broken, up to 16 copies.

The requirement is to run Exchange 2010 on a Windows 2008 (R2) Enterprise Server because it uses some components/api’s of the failover cluster service.

How to

To create a “DAG”, go to Organization Configuration, choose Database Availability Groups, right click and select ‘New Database Availability Group…’ type in a name for it, specify a Witness Server (usually the CAS/HUB server) and point out the Witness Directory like C:\fsw. It can be used on other servers to, don’t forget to add the Exchange Trusted Subsystem security group to local admins on the server that should act as FSW and allow WMI if the firewall is enabled.

When it’s created, right click the newly created DAG and choose ‘Manage Database Availability Group Membership…’ select Add button and add in the mailbox servers that should be part of the DAG.

The IP address for the DAG cannot be set in the GUI so it has to be done in PowerShell with the following command:
Set-DatabaseAvailabilityGroup DAGNAME –DatabaseAvailabilityGroupIpAddresses IPADDRESS

Now it’s time to add the other server to hold a passive copy of the database, it done by either Management Console or PowerShell. I prefer to do it in GUI.

Go to Organization Configuration and select Mailbox, and choose ‘Database Management’ tab.
Now select the database that you want to make a passive copy of, right click and choose ‘Add Mailbox Database Copy…’ a wizard is shown with a browse button, click that one and select the server that should hold the passive copy of the database.

If you want to change which server that has the active database, just select the database and choose ‘Move Active Mailbox Database’ and a wizard is shown.

A picture is shown below how to move the active mailbox database to another server


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