Question of Exchange 2010 DAG

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Joe Tam

Dear sir,
I have a question about Exchange 2010 DAG, please suggest the practice:

Environment: 2 Sites

Site1: Main office: Windows 2008R2 AD + 2 x Exchange 2010 with DAG

Site2: DR: Windows 2008R2 DC + 1 x Exchange 2010 (DAG with 2 x main office of Exchange 2010 server)

Site1 and Site 2 are interconnected by 2M/2M Site to Site VPN link.

Q1: Is it better to configure DR site segment address belong into to same AD Site in Windows Active directory site and service, or define as 2 x differents site?

Q2: In this case, should we enable the DAC setting which not allow false action of Exchange DB failover from main office to DR site? Or can I configure DAG that it can only allow to perform automatic failover only in main site? (i.e. EXServer1 down, those database will failover to EXServer2, but no to EXServer3 in DR) ?


Brian Day MCITP

A1: It is better to configure separate AD sites for many reasons.

A2: I always suggest DAC be used. You can also activation block the copies on the DR server if you'd like to.

See this link to learn how to enable an activation block on a database.

Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.

Joe Tam

Dear Brain,
Thank you for your email.
Actually I have gone through some article about DAC, but in the 2 sites only envionment. If I have configure DR site server as activation block. Why I should configure to enable DAC ? Or it can be maintain automatic failover function for Site1 ?



Quote: “If I have configure DR site server as activation block. Why I should configure to enable DAC ?”

When site 1 is down, and mail system is being switchovered on site 2. However, if the servers in the site 1 have been recovered and the network is still disconnecting between two sites, then, the split brain syndrome will appear (Assuming the majority of the voters are in the site 1). You should enable DAC because it can prevent split brain syndrome

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