Exchange Server 2010 Database Availability Group Installation Step by Step

Microsoft Exchange Server 2010 introduced a new high availability feature called the Database Availability Group (DAG).  This tutorial describes how Database Availability Groups work in Exchange Server 2010, as well as demonstrating the steps for deploying a DAG using Exchange Server 2010 SP1 and Windows Server 2008 R2.

Exchange Server 2010 Database Availability Group Overview

A Database Availability Group is a group of up to 16 Exchange Server 2010 servers that are installed with the Mailbox server role.  Each server that is a member of the DAG is capable of hosting active or passive copies of mailbox databases that reside on servers in the group.

For example, a Database Availability Group may consist of three Exchange Server 2010 Mailbox servers, each configured with a single Mailbox database.  Each server that is a member of the DAG can host either an active or passive copy of each of the three total mailbox databases.

Exchange Server 2010 Database Availability Group Example
Exchange Server 2010 Database Availability Group Example

The foundation of an Exchange Server 2010 Database Availability Group is Windows Failover Clustering.  However unlike traditional Exchange server clusters which existed in an active/passive state, and in which the entire cluster group needed to failover to an alternative node together, with Exchange 2010 DAGs each mailbox database can failover (or switchover, if it is a deliberate move) to another DAG member independent of the other mailbox databases in the DAG.

This means that any given Mailbox server in the DAG can host all, some or none of the active mailbox copies at any given time.  This capability provides two immediate advantages over previous clustering models:

  • All of the Mailbox servers within the Exchange 2010 DAG can be active and in use at all times to some capacity
  • Each mailbox database can failover/switchover when necessary without impacting the mailbox users connected to other mailbox databases within the DAG, for example when installing updates on DAG members

Understanding Quorum for Exchange Server 2010 Database Availability Groups

Because the Database Availability Group utilizes an underlying Windows Failover Cluster the concept of quorum applies.  If you are not familiar with quorum consider it as basically a voting process in which a majority of voting members must be present to make a decision.

For a cluster this means that an odd number of members must be involved in the voting process for a majority decision to be made.  How this applies to an Exchange Server 2010 DAG is that if you deploy a DAG with just two Mailbox servers as members (or any even number up to 16), then neither server is able to determine by majority vote whether it should make its own copy of a given mailbox database active.

To achieve quorum for a DAG with an even number of member servers another server in the same site is designated as a File Share Witness for the cluster.  This is typically a Hub Transport server though it can technically be any compatible Windows server.

Database Replication in Exchange Server 2010 Database Availability Groups

There are two ways that mailbox database replication occurs between Exchange Server 2010 DAG members.

In Exchange Server 2010 RTM “file mode” replication is used.  With file mode replication as each transaction log is written and then closed off (once it reaches 1Mb in size) it is then copied to each member of the DAG that also holds a copy of that mailbox database.  The other members receive the file into their replay queue, and then replay the transaction log file into their own passive copy of the database.

File mode replication works fine but has an obvious shortcoming in that any transaction logs that have not yet been shipped to other servers in the DAG can be lost if the Exchange server hosting the active database copy fails.  In those cases one of the other DAG members is able to bring their copy of the mailbox database online and then request missing emails be resent from the transport dumpster of Hub Transport servers within the site.

In Exchange Server 2010 SP1 file mode replication is used to bring mailbox database copies into sync with each other (eg during the initial sync process when a new database copy is added).  Once they are in sync the DAG members switch to “block mode” replication.  In block mode replication each database transaction is written to the log buffer on the active server and also sent to the log buffer of DAG members hosting passive copies of the database.

When the log buffer becomes full each DAG member then builds their own transaction log files from their own log buffer.  Block mode replication has an advantage over file mode replication in failure scenarios, because each DAG member is completely up to date with all changes to the active database.

Note that Public Folder databases can reside on Mailbox servers that are members of a Database Availability Group, however they are not replicated by the DAG itself.  Instead you must use Public Folder replication to provide redundant copies of Public Folder databases.

Other Advantages of Exchange Server 2010 Database Availability Groups

Before we proceed with an example of how to install an Exchange Server 2010 DAG I will also mention some of the other advantages of Database Availability Groups.

  • Unlike previous versions of Exchange Server (particularly Exchange Server 2007) Exchange Server 2010 has just one high availability feature for Mailbox servers for all high availability deployment scenarios
  • When you create a Database Availability Group the underlying Windows Failover Cluster is automatically created and configured for you
  • A Database Availability Group can be created at any time without requiring Exchange Server 2010 to be removed and reinstalled from the server, unlike previous versions that required that clusters be established first before Exchange was installed
  • Exchange Server 2010 DAG members can host other server roles, unlike Exchange Server 2007 that prevented clustered Mailbox servers from hosting other roles

Exchange Server 2010 Installation Step by Step

In this tutorial I will demonstrate the installation of an Exchange Server 2010 Database Availability Group on Windows Server 2008 R2.

For this tutorial the following Exchange servers have already been installed.

  • EX1 – Exchange Server 2010 SP1 Mailbox server
    • Primary interface: 192.168.0.32/24
    • Secondary interface: 10.0.5.1/30
  • EX2 – Exchange Server 2010 SP1 Mailbox server
    • Primary interface: 192.168.0.33/24
    • Secondary interface: 10.0.5.2/30
  • EX3 – Exchange Server 2010 SP1 Client Access and Hub Transport server
    • Primary interface: 192.168.0.34/24

Note: for details of how to deploy these server roles see Installing Exchange Server 2010 Pre-requisites on Windows Server 2008 R2 and Installing Exchange Server 2010.

Exchange Server 2010 DAG Tutorial Setup
Exchange Server 2010 DAG Tutorial Setup

Each of the Mailbox servers has been configured with its own mailbox database.

  • EX1 – Mailbox Database 01
  • EX2 – Mailbox Database 02

Note: in Exchange Server 2010 each mailbox database must have a unique name within the organization.

Because the Mailbox servers are configured with dual interfaces it is important to make sure that the secondary interface is not configured to register itself in DNS.  Open the TCP/IPv4 properties for the secondary interface one each server, click the Advanced button, navigate to the DNS tab and untick Register this connection’s address in DNS.

Open the Advanced TCP/IPv4 Properties
Open the Advanced TCP/IPv4 Properties
Disable DNS registration for the secondary interface
Disable DNS registration for the secondary interface

Creating the Database Availability Group

Log in to one of the Mailbox servers and launch the Exchange Management Console.  Navigate to Organization Config/Mailbox and choose New Database Availability Group from the action pane.

Create a new Exchange Server 2010 Database Availability Group
Create a new Exchange Server 2010 Database Availability Group

When the New Database Availability Group wizard starts give the DAG a name, specify the Witness server, and also specify the file path for the Witness server to use.

New Database Availability Group Wizard - Basic Info
New Database Availability Group Wizard - Basic Info

Click on the New button to create the new Database Availability Group, and then click Finish to close the wizard.

Adding Database Availability Group Members

Right-click the newly created Database Availability Group and choose Manage Database Availability Group Membership.

Manage Database Availability Group Members
Manage Database Availability Group Members

Click the Add button and select the Mailbox servers that you wish to make members of the DAG.

Select Mailbox Servers to become Database Availability Group Members
Select Mailbox Servers to become Database Availability Group Members

Click the Manage button to commence adding the Mailbox servers to the DAG.  This involves installation and configuration of Windows Failover Clustering on the servers, so it can take a few minutes to finish.

After it has finished the next step is to configure the DAG networking.

Configure Database Availability Group Networking

Right-click the newly created Database Availability Group and choose Properties.

Open the Properties of the Database Availability Group
Open the Properties of the Database Availability Group

Select the IP Addresses tab, click the Add button and add a static IP address for the Database Availability Group.

Adding IP addresses to an Exchange Server 2010 Database Availability Group
Adding IP addresses to an Exchange Server 2010 Database Availability Group

You will notice that the Database Availability Group has been automatically configured with DAG networks for the subnets that the DAG members have network interfaces connected to.

Exchange Server 2010 Database Availability Group Networks
Exchange Server 2010 Database Availability Group Networks

Open the Properties of each DAG network and configure them with meaningful names.  If you have configured your network to have a dedicated replication network for the DAG then you should disable replication on the DAG network that is intended for MAPI communications (ie client connections).

Exchange Server 2010 Database Availability Group Networks Configured
Exchange Server 2010 Database Availability Group Networks Configured

Adding Mailbox Database Copies to DAG Members

With the Database Availability Group established and the networking configured you can now add mailbox database copies to other DAG members.

In the Exchange Management Console navigate to Organization Config/Mailbox and choose the Database Management tab.  Right-click a mailbox database and select Add Mailbox Database Copy.

Adding a Mailbox Database Copy in Exchange Server 2010
Adding a Mailbox Database Copy in Exchange Server 2010

Click the Browse button and choose the Mailbox server to add the database copy to.

Add Mailbox Database Copies to an Exchange Server 2010 Mailbox Server
Add Mailbox Database Copies to an Exchange Server 2010 Mailbox Server

Click the Add button to add the mailbox database copy and then click Finish to close the wizard.

The Exchange servers will now commence seeding the replica servers with an up to date copy of the database and all of the current transaction log files.  Depending on the amount of data to be replicated this may take some time.

Status of the Database Copies for Exchange Server 2010
Status of the Database Copies for Exchange Server 2010

Repeat the same process for any other mailbox databases you wish to add database copies for.

Configuration of the Exchange Server 2010 Database Availability Group is now complete.

Comments

  1. Dinesh Silva says

    Hi there,

    Highly appreciated your DAG configuration article and your plain English explanation is very helpful.

    Thanks and awaiting for more new articles :)

    regards

  2. Santosh Kumar says

    Really very effective presentaion shared.. to follow this , who is having less knowledge of DAG can also configured easily.

    Thanks.. Buddy . keep it UP !!

  3. Sam says

    Good Article.I just had a doubt , it the there is Clustering between the servers, how does the external world know the Exchange server name? What is EVS Name Here ? Which will be used to configure the outlook for end users if required ?

  4. Brenda says

    Paul

    When I go to add the database copy, it does not give me the option of the other mailbox role server to choose from, it only shows the the current mailbox server that the database is sitting on

      • Brenda says

        It does not show up there as well, ( I probably should have started with that) I created the DAG on EX 2 when, and when I go to manage database database availability group membership to add EX1 it does not give me the option to EX 1 as well

      • says

        Ok so lets step back a little and try to work this one out. First the basic stuff:

        Is EX1 an Exchange 2010 server?
        Is EX1 installed as a Mailbox server?
        Is EX1 already a member of an NLB cluster?
        Is EX1 installed on Enterprise version Windows Server?
        Does EX1 appear as you’d expect in Get-ExchangeServer output?
        Is the EX1 event log clear of errors?
        Does EX1 have any other signs of being unhealthy?

      • Brenda says

        383 >> Client Access/ Hub >> Enterprise >> 14.1
        384 >> Client Access/Hub >> Enterprise >> 14.1
        382 >> Mailbox >> Enterprise >>14.1
        381 >> Mailbox >> Enterprise>>14.1

        Yes, it is Exchange 2010
        EX 381 and EX 382 are both mailbox role servers
        383 and 384 are in NLB
        I have to add that it is the other way around with 382 if I create a DAG on 382 and try to add 381 it will not show up – Thanks for your help !

      • says

        Hmmm. Well, a mailbox server can only be a member of one DAG at a time. I don’t suppose you’ve accidentally created two DAGs, and so the other server is already a member of a DAG and can’t be added to another one?

        If you run Get-DatabaseAvailabilityGroup do you see one or two DAGs in the results?

  5. Great Article says

    Hi Paul, This is really helpful article for exchange administrator, to understanding DAG feature in depth for who wondering here and there..This really make me comfortable in case of DAG functionality.

    Hope, you will keep posting such article in future also.

    Regards
    Rajnish

  6. vubinhsg says

    hi Paul,

    very usefull and easy to understand with illustrations. i have a question. do we have to install the 2 mailbox-server-role servers from the begining and create the DAG, add the 2 MBX servers at the same time ? or we can create a DAG and add one MBX server then add the second MBX later ? as we know that the DAG can tolerate one MBX down for a short time (with the witness share evidently).

    • says

      You can create the DAG and add members at any time you wish, even after you’ve already added mailboxes to the databases on those servers. Microsoft calls this “incremental deployment”.

  7. jmills says

    Regarding the DAG and Replication network, we’ve been having issues setting these up and replicating across. I’ve seen several recommendations regarding certain protocols to disable for the Replication Adapters which did not change our results. Also some stating to put DHCP enabled for replication adapters? Following your guide was not sure on your experience with the specifics. But also to be clear when setting up the IP address of the DAG, it should be an IP on the Production Network, NOT replication?

  8. oopk says

    This is really helpful article for Exchange Server Installation with Database Availability Groups. Simple way of create nods because this steps GUI based .

  9. rahul says

    i made a VM of exchange server 2010 sp2 which is connected to a child domain i.e customer and nw i want to make another vm of exchange server in which i want to install DAG and this shoud also connected to that child domain(customer). plsssssss tell me, what to do?????? plssssssssss

  10. jagadeesh says

    HI thanks for above article we’ve successfully created DAG in Exchange 2010 SP1

    Do u have any article how to install Exc 2010 SP2 in a Child domain controller

    Please help me on this i’m new to this concepts

    Thanks

  11. Simon says

    Hi Paul,
    Can I ask your advice on something – I’ve an existing DAG with 2 MBX servers but after installing Exchange SP2 parts of the underlying cluster are failing: When i look in Failover Cluster Manager (2008R2) i see that the Cluster Name (dagarray) is in a failed state and I think this is because there used to be an IP Address as a dependancy which has now vanished. I’ve tried removing and adding that IP address back in through EMC but it doesn’t solve the issue though EMC warns me that ‘dagarray’ is not online.

    I’ve Googled a lot and am beginng to think that I need to create a new DAG so that Exchange resets everything nicely. I’m a little concerned about this as I have 700 mailboxes spread across 13 databases. If I switchover all the databases to one of the MBX servers and then create a new DAG, remove that server from the old DAG and put it in the NEW DAG will the mailboxes be okay? If I then move the 2nd MBX server out of the old DAG and put it in the new DAG and then delete the old DAG, will everything be happy?

    Any advice you can offer woudl be much appreciated,

    thanks.

  12. says

    Paul,

    Great wite up on DAG. I wanted to implement this feature in our datacenter and wanted to ask you some questions on setting up 2 Exchange 2010 server.

    Office- Domain A- 2008R2 and Exchange 2010

    1: Datacenter- Do I create a fresh domain without connecting to Office domain? Totally seperate domain name?
    2: Where do I attach the 2nd datacenter Exchange server? the main office or 2nd new domain?
    3: If for X reason 1st Domain / Exchange server goes down, how would you configuer to 1st repoint all outlook clients to datacenter AUTOMATICALLY?

    Thanks for any insight on this.

    Jerry

  13. Ozz says

    Can you advise if it’s possible to set this up as a POC on VMs?
    Also how much time would be required for the installation and testing on such a scenario?
    Thanks for the detailed post.
    Cheers,

    Ozz.

  14. Ashraf Tammam says

    Thanks

    but is it possible for the same servers (EX1 and EX2) to have Client Access and Hub Transport server roles installed with load-balanced CAS Array configured on them with DAG?? and EX3 acts as a normal file server???

    • says

      NLB is not supported when the server is also a DAG member because the DAG uses Failover Clustering, which is not supported to co-exist with NLB.

      Basically NLB and Failover Clustering can’t be used on the same server, so an Exchange DAG member can’t also be an NLB member.

  15. Marc Wenger says

    Thanks – this is very helpful, but a question about IP address segments. In your example you have the replication running in 10.0.5.0/30 and primary running in 192.168.0.0/24. Could I have replication running in the same subnet as the primary?

  16. Ritchie Beltran says

    Thank you for the article. Quick question regarding the replication network. If I have a 2 node DAG, am I able to just connect the 2 servers directly via ethernet instead of the replication network going via a switch since the replication network don’t need to any other server?

  17. Herb Mays says

    I have a situation where a previous admin setup a DAG and CAS array with the same name and IP, so the DAG is called DAG and CAS array is called DAG with the IP of the Database Availability Group. Surprisingly enough the users are having RPC connection issues to the Exchange servers. My thought is to just redo the actual DAG and leave the CAS array since clients are connecting to the CAS array name already. Have you run into this before or have any articles?

  18. says

    Another great article, thanks.

    I’ve inherited a pickle of a system, 2 x Win 2012 DCs, with Exchange 2010 SP1 installed on them both and configured in a DAG that appears to never of worked properly! I think I’m ok with removing one of the DAG members assuming it works ok.

    What is the process of removing the last member of a DAG?

  19. Mark says

    I have a cross site two mailbox server configuration with DAG. Each MB primary network interface has a DHCP reservation. DAG has dynamic DHCP assigned. Is it normal for DAG to register its IP address for both DAG and MB Server name? e.g. Clients of one server are connecting via outlook to the IP of the DAG vs the IP of the MB Server name.

    • says

      The server NICs should have static IP addresses, not DHCP reservations.

      The DAG IP can be dynamic, though I prefer to assign a static IP to it (one per subnet that contains DAG members).

      The DAG name itself will be registered in DNS and should update itself if the PAM role moves to a different subnet. However clients do not connect to the DAG name, they connect to the RPCClientAccessServer name.

      So the only way I can think that you would see clients showing connections in Outlook to the DAG IP is if you’ve used the same name of the DAG itself as the RPCClientAccessServer on your mailbox databases, which is not a correct configuration.

  20. Tom says

    If its possible to create DAG, in which 3 exchanges(2010) is present in different domains and all the servers roles is present in the exchange.

  21. Tom says

    or is it possible to create DAG, in which 3 exchange(2010 sp1) is present in same domain and all the server roles is present in the exchange ?

  22. Sab says

    Thanks Paul for another great article, it seems pretty simple and clean to understand.

    According to the above scenario its 3 servers, can we setup a DAG using only 2 servers, can we run both CA, HT and Mailbox role on each servers and run that as DAG

    • says

      Yes, a DAG can have anything up to 16 members.

      If you multi-role the servers you just can’t use NLB for CAS Array, as it isn’t supported on servers that are also DAG members. A hardware or virtual load balancer is required instead.

      • Sab says

        Thanks Paul for the prompt response,

        If we have to go with a virtual Load Balancer, what would you recommend, what about KEMP LoadMaster? Thanks

        • says

          I have experience with both Kemp and F5. Both are fine. I recommend you do your own evaluation (they have free trials) based on your budget and business/technical requirements.

  23. Doug says

    One the DAG is established and functioning (not a production environment at this time), is it safe to change the IP of the DAG name, to conform with new IP role assignments? For example:

    Old messaging IP = x.y.48.47
    New messageing IP = x.y.48.147

    Assuming the same ip space and subnet.

  24. Kyle says

    Paul

    Found your blog recently and I am finding a lot of useful information to manage my Exchange environment.

    I have a situation coming up and wondered if you might offer comment or advice. I followed this post as I setup my Exchange platform. I have three – two server DAG clusters. Each cluster has a MAPI network and a DAG network. The MAPI network is tied to a 1GB switch and the DAG network is tied to a 10GB switch. Currently replication is configured on the DAG network.

    Due to a SAN upgrade, our 10GB switches need to be reconfigured, which will cause a reboot and outage. Can I move replication to the MAPI network to avoid having to shutdown the servers during this switch reconfiguration? Will moving replication to the MAPI network help avoid the servers trying to failover when the 10GB switches start rebooting?

    thanks for any advice you might have.

  25. John says

    Hi Paul,
    Can I use this method to add two trusted Domain for sync between them, Domains have different names,
    Thanks

  26. Robbie Deol says

    Thank you Paul. It is the best article on DAG out there. Diagrams make it very easy to understand.

    thank you.

    /Robbie

  27. Agust Muharyadi says

    Hai Paul,

    I would like to ask you, for the IP address of DAG server above is 192.168.0.39? is that IP address of mailbox server 2? need your advice.

    I have 2 mailbox server, IP address of mailbox server 1 is 10.252.26.8 and IP address of mailbox server 2 is 10.252.26.10. For IP of DAG server, what will i choose for IP of DAG server?

    • says

      The DAG itself has its own IP address separate to the IP addresses of the servers that are DAG members. You should assign it an IP address in the same subnet as the MAPI (client-facing) IP addresses of the DAG members.

  28. Jake Jacob says

    Paul thank you!

    Great great great!. Quick question. I have one Exchange 2010 SP1 server (all roles). Looking into deploying a DAG as in your scenario. EX3, in your above example, is a dedicated server that serves as the witness server and quorum location. Do i really need a 3rd Exchange server for this or can i use an existing MBX server? If i wanted to also setup and edge transport server in a DMZ, would that be a completely different server?

    i think i know the answer, but i’m trying to minimize the licensing requirements without sacrificing the design too much. It sounds like i need 4 licenses for Exchange and Windows respectively.

    thank you!

    • says

      The File Share Witness can be another Exchange server as long as it is not a DAG member. You can also use any other server in your network that can host a file share. The FSW isn’t the “quorum location”, it is just an extra vote in the cluster for determining whether quorum (a majority of nodes available) can be reached.

      The general recommendation is to use another server that is fully in control of the Exchange admins.

      In small IT depts obviously that is not going to be a big deal and you could just use pretty much any server.

      It is possible, but not recommended, to use a domain controller as the File Share Witness.

      Edge Transport always needs to be installed on its own server. That role doesn’t co-exist with any other role.

  29. ZAHOOR RATHER says

    Hi,
    Thanks for the article.
    Actually i have two Exchange 2010 SP3 server located on two diferent AD sites wiht typical inst. Roles.
    Now i have to deploy DAG using a witness server.

    How could i manage the *over[fail over/switch over if one of the server has jsut failure in network or link between the sites is down etc.

    What happens in this case.

    thanks.

    ZAHOOR

  30. John says

    Hi Paul,

    I have inherited a system that has been partially setup with a DAG, there are 2 mailbox servers running, the CA server is on a different subnet for some reason. The DAG has an IP address set but no members, if I check in EMC I can see the DAG on the CA server, but no networking has been configured. NIC2 in EX1 has a static IP address NIC2 in EX2 has DHCP and both are registered in DNS. If the DAG is not actually being used would it be easier to remove completely and reconfigure with a new DAG without impacting the exchange environment?

  31. Gaurav Passi says

    Hi Paul!

    First of all…IT’S AN AWESOME ARTICLE! The best DAG article that I’ve read so far :)

    I’m new to your blog and loving it already.

    I’m about to deploy my first DAG with 2 Exchange 2010 SP1 (Typical Installation) with Windows 2008 R2 Enterprise. Using a File Server for Witness.

    I’ve few quieres. Can you please be kind enough to answer them if you’ve few minutes:

    1. How can I control the DAG sync?
    2. Will the outlook clients need to be reconfigured after DAG creation to or they’ll be redirected automatically?
    3. What changes will be required on the Spam filter, Internal DNS, Public DNS and Firewall to accommodate the changes made for DAG?
    4.What happens when the primary site goes down and you lose 2 votes at the same time? Will the backup exchange take over or the exchange environment will go down and I’ll have to perform a manual site failover?
    5. If a manual site failover is required then what things need to be taken under consideration and how to revert back the changes once the primary site is back online?

    Regards,
    Gaurav

    • says

      1. You don’t need to control the DAG replication.
      2. Nothing is required.
      3. Nothing is required.
      4. There is no automatic site failover in a disaster situation.
      5. Multi-site DAG design and failover/recovery is a complex matter that has been thoroughly documented on TechNet. It is more than I can answer here, you really do need to just go and read the documentation.

  32. says

    Dear all. I a new to exchange 2010 but I have a new challenge to complete. We have 2 CAS (say CAS A & CAS B) & 2 MBX Server (MBX1 & MBX2) in our environment at Location A. Due to some problem, and DR plan, we like to create another CAS Server C & MBX server C in Location B (Location A & B are connected by dedicated fibre @ LAN). And after done, we would like to move the databases from and other settings from CAS B & MBX B to CAS C & MBX C. After done, we like to decommission both CAS B & MBX B.

    I like to ask the experts here to guide me step by step how to accomplish this. Thanks in advance.

  33. Dave says

    Hi,
    my question is simple..

    can i change the time before my dag swith to the second dag on my second data center on a different subnet..

    because now, on my first dag i have 2 server but if my master crash the dag switch to the second subnet…
    my slave server dont mount the database automatically.
    any suggestion ?

    • says

      The DAG uses a process called Best Copy Selection to determine which database copy it should failover to when the active database copy becomes unavailable. There are a lot of factors on Best Copy Selection, but generally speaking you can influence it by setting the Activation Preference of each database copy.

      You can also block automatic database activation on the server(s) in the second datacenter.

  34. Kim Kovacs says

    Hi Paul – I’ve had a 2-mailbox DAG running for a couple of years, and now I’m getting ready to retire the hardware & move the servers to VMs.

    MB1 & MB2 are running Exchange 2010 SP3 on Windows Server 2008 R2.
    MB3, the one I’d like to add, is Exchange 2010 SP3 on Windows 2012 and is a virtual guest.

    All three mail servers are visible in the console, and I can create mailbox databases on the new server, no problem. However, I just can not get MB3 to join the DAG. When I try to add it I get a vague error “Failed to initialize cluster with error 0×80004005.”

    Is there any compatibility issue you can think of that would be causing this problem? I’ve checked permissions, ran the cluster config check on the VM, confirmed the IP addresses are fine – just can’t find what I’m missing!

    Any thoughts would be sincerely appreciated.

  35. Parag Thorat says

    Dear Paul,

    I have to migrate exchange 2003 to Exchange 2010 (On new server 2008 R2). Please guide me the best practice for this migration.

    Rg,
    Parag.

  36. Gaurav says

    Hi Paul,

    Quick Question :)

    After I create a DAG, add the exchange servers to the DAG and then I select ‘Add Mailbox Database Copy’ option. When I select that option, DAG will create the copy of the original mailbox database on the 2nd exchange server but will it create the copy of the database in the default location i.e. C:\Program Files\Microsoft\Exchange\v14\Mailbox Database or will see the path of the original mailbox database on the 1st server and will use that path.

    For example, my exchange databases are on a separate drive with E: as the drive letter.

    Will DAG create the copy on the E: of the 2nd exchange server or will go to the default location on the C: drive.

    Regards,
    Gaurav

  37. Bob Collins says

    Hi Paul,

    Great DAG article, it sure clears up many things for me. I have a question about building a DAG and performing the Database Copy. The DAG I have was built prior to my arrival at this location and I am trying to rebuild/get it working again.

    I have a three server DAG and my primary database needs to be copied to the second and third MBox servers, however when I copy the database via EMC, the copy will fail when the receiving MBox server halts with an out of space on it’s vmdk.

    Is there a spatial headroom number/multiplier when making this copy? My db is just over 500GB, however my database location on the second MBox server is at 996GB free space. It seems like it should not fail, but it does? To that end, must the storage location receiving the DB be the same size or larger than from where it is sent?

    I have otherwise been able to match the system (C:) and the log file drive (L:) sizes. The mailstore drive (S:) size is smaller than the source’s. Will this matter? Am I missing something?

    For that matter, will the database copy know to place the logs in the proper log file location on the recipient?

    Thanks for your thoughts and consideration.
    Bob

    • says

      Each DAG member should have the same storage layout in terms of drive letters/mount points and capacity.

      If a database resides on E:\DB1\db1.edb on one server, and you add a copy of that database to another DAG member, that second DAG member will store it in the same E:\DB1\db1.edb path. Same goes for the logs.

      The fact you’re using VMDK makes me think the problem may be that the VM datastore itself is full.

      • Bob Collins says

        Hi Paul,

        Thanks so much for the reply. I had suspected such, but wanted clarification to that.
        I will pursue the VMDK side of this equation.

        Thanks again!
        Bob

      • Bob Collins says

        Hi Paul,

        I wanted to follow-up and let you know how my systems fared based on your suggestions. It did turn out we had “orphaned” snapshots eating up some space on our datastores. To clear them, we used the Consolidate tool from VSphere in the snapshot management area. Once that was complete, things settled down and the copy was able to complete properly.

        I now have a proper DAG with a second DB copy in a Healthy state.

        Thanks for the pointer and for all your articles I find myself reading often.
        Bob

  38. Ken Jones says

    Paul,
    Hope you can give some direction currently Have Exchange 2010 SP1 setup As a DAG each is a VM. Also have 2 more VM’s as the CAS servers. Now we are moving off static VM host to Hyper-V Fail-over Clustering. What is the Best way to configure this. I was told I cant put the DAG on the Hyper-V cluster but Can i put one on each of the cluster nodes and just run them from the regular Hyper-V console not making them Highly Available via the Hyper-V Fail-over Cluster?

    • says

      Microsoft publishes quite detailed guidance on mixing virtualization, clustering, and Exchange 2010 DAGs. It is more than I can cover in a comment here. You’ll need to do a bit of reading.

  39. Navishkar Sadheo says

    Hi Paul

    Thank you for your article.

    Can you assist me with the hardware load balancing part.

    I have 3 mutil role exch 2010 servers. 1 at each site.

    I am planning on adding 3 additional multi role servers, 1 to each site.

    Problem is if I implement DAG then I cannot create my CAS array using WNLB and need to use hardware load balancing.

    Can you perhaps point me in the right direction?

    • says

      There are several vendors I’ve worked with in the past – F5 and Kemp for example. What you should really do is gather your business and technical requirements, and your budget, and then take advantage of the trial offers from a few vendors to try them out and find one that fits your criteria and that you’re comfortable with administering.

  40. Jason Cramer says

    Hi Paul,

    I don’t see anything about what to do about not being allowed a default gateway on more than one NIC on a Windows server. Did you already describe using route ADD or the equivalent netsh commands in a different article?

    Thanks for the great article BTW.

    Cheers,
    Jason

  41. Ray says

    Hey Paul,
    how about the certificates? if you have a server on a secondary site do you need another SSL for that server as well?

    • says

      In the context of the DAG, which is a feature of the Mailbox server role, no there is no SSL certificate required.

      However a secondary site does imply that you will have Client Access server(s) in that site as well. Yes, each CAS will require an SSL certificate provisioned (the same cert for all CAS is feasible depending on your scenario).

  42. Brian Ganino says

    Hello Paul,

    Great article!

    I have a question related the IP address used.

    I have a DAG working on my exchange environment and I’m adding a new mailbox server for DRP propose. This MBX server will has only one IP address. Could I add this server as member of the existing DAG? What could be the problem if I don’t add a replication IP address?

    Thank you.

    • says

      Yes you can add new servers to an existing DAG.

      Replication networks for DAGs are not mandatory. They are only if you have a specific need to segregate your replication traffic from client traffic (eg for bandwidth management).

  43. Shawnicles says

    Just had a question about the DAG Witness server.

    I have two exchange servers with typical roles installed at two sites. I am using a third non-exchange server (like in your 2013 article) to be the witness server for the DAG.

    Does this server need to be Server Enterprise as well like the two exchange servers?

    Thanks!

      • Shawnicles says

        Thanks for the quick reply.

        Since I haven’t seen any specific articles related to using a non-exchange server to be the witness server for DAG in Exchange 2010. Am I right in assuming it will work? I’ve created a new DAG, and specified that server to be the witness and it has created the DAG.

        I added the local admin group membership, feature and firewall exception. Is there anything else I should be aware of that could be different in 2010?

        Thanks!
        Shawn

  44. Ampletrix says

    Hello Paul,

    Thank you for the great article! Fantastic work.

    I’ve inherited an Exchange environment with 4 Exchange servers: 2 MB servers in a DAG, with two CA and HT servers.

    The previous admin configured the DAG with everything seemingly working fine. The DAG name is DAG1, with both MB servers (Exch03 and Exch04) as members, and Exch01 (CA and HT) as the witness server.

    While planning on adding a new database to the DAG, I’ve noticed that the DAG has no IP address configured. Would you mind helping me out with the implications of the DAG not having an IP configured please?

    This has been the case for nearly 8 months now, and we haven’t had any major issues.
    Thank you.

    Ampletrix.

  45. Imran says

    Hey Paul ,
    Thanks a lot for such greate post, YOUR THE MAN and always helpful for me and rest.

    I need your help regarding my network, that is :
    I have an exchange server by name of exch1 with 10.63.109.121 ip that is avilable for my outside with ip address of 10.63.108.11 (NAT feature on ASA Firewall ) and now i create other exchange server with 10.63.109.120 which is not avilable in my outside exch1 and exch2 have DAG configured only exch1 database copy is in exch2 my DAG-001 ip address is 10.63.109.19
    More information : my exch1 replica is 192.168.1.1/30 and exch replica LAN card ip is 192.168.1.2/30
    kindly answer me following questions:

    1: Is my DAG ip is okay and from proper network?

    2: if my exch1 goes down how outside people will reach to my exch2 or (voice versa)

    1: same as i told u exch1 MB DATABASE copy is in exch2 if my exch1 goes down how LAN exchange clinet of my network will reach to them own mailbox through outlook?

      • Imran says

        Thanks for quick reponse,
        i review the link you post up,
        my questions is ;
        do i need other exchange server with CAS role or one of my current DAG servers can be my CAS too?
        i had verfied both have CAS role intalled.

        regards

        • says

          You can use the CAS roles installed on your existing DAG members. You should load balance CAS traffic to *both* servers if you want high availability.

        • Imran says

          Hello, Paul I face a new problem its:

          I configured DAG in my exch1, it have send connectors and receive connectors and all other required setting.
          Main point is : its Allowed and known to my all outside sub office through ASA firewall its IP been NAT but my exch2 server is not allowed to out side and unkown to out people even local users but it already replicated all settings from exch1 after installation so the problem is culster failover selected exch 2 as current host server when i send email to outside its been stop in queue coz exch2 IP is uknown to out people so how can i change it how to solve this issue?

          thanks in advance
          imran from afghanistan

  46. Imran says

    Hey Paul i got an urgent question :

    I have to 2 exchange everything is okay i follow all your notes about CAS, DAG and DNS Round robin everything is okay but big issue is :
    my exch1 is interduced to out side and all outside people defined exch1 NAT ip on them receive connectors but now when my clients send email it goes to exch2 queue please let me know how to configure that mails go through exch1 queue i don’t want out side people to know i have exch2 whenever any issue accure i will change ASA object ip address from exch1′s ip to exch2 but currently i want exch1 to communicate?
    its my last step of work rest i am done,

    thanks so much for all suppports
    imran from afghanistan

      • imran says

        thanks paul brother
        can u please tell me the steps or commmands or recommand any link?

        regards,
        imtan from afghanistan

  47. Bob Collins says

    Imran, could you not put a send connector on EXCH2 to send all mail to EXCH1. EXCH1 send connector would be to the outside?

    Or make EXCH1 the smarthost for EXCH2.

    • Imran says

      Bob Brother,

      both exchanges are doing replication (settings/ DAGs) if i create a connector in exch2 to send all stuff to exch1 it will replicate back to exch1 hahaha kindly if you know any other way let me know,

      thanks for nice comment

      imran from afghanistan

      • Bob Collins says

        Oh right! Too early for me this morning, must have more coffee.
        My environment is similar, yet we send all outbound mail to our ProofPoint filter then it goes out.

        Will have to wait til better insight from the smarter guys here. :-)

        • Imran says

          Aw Oright I hope you had a good day :D

          buddy I try something new I put both exch1 and exch2 in SORUCE SERVER tab of all send connectors its working now but i am not sure wheather the cause is this or anything else LOL
          however THE MAN THE BOSS (Paul) is here he can support us very well as he did 100s times in past ;)

          cheers,
          imran from afghanistan

  48. shady elmasary says

    Hello Paul ;

    Thanks a lot for these post , it is valuable information .

    I have a question related to DAG across different sites

    I want to know the best way to implement DAG FOR EXCHAMGE 2010 across 2 sites ,

    I have 3 exchanger server in one site in DAG ,with 300 gb database size

    but I want to implement exchange server 2010 in a new site and this will be my fourth exchange server and will be a member on my existing DAG in the head office

    the new site is linked to my head office using ipvpn connection which is 6 mb ,

    what is the best way to implement the new exchange server in the new site to join the existing DAG .

    is there is any problem related to DAG in this scenario , consideration , and the way to implement it in the new site ?

    Thanks again for your post

    • says

      This is more than I can answer in a comments thread. TechNet has detailed documentation on the requirements for multi-site DAGs such as network speeds etc. You’ll also need to read up on DAC mode.

  49. Shady elmasary says

    Hello Paul ;

    Thanks a lot for your help , I found too many articles in tech net regarding DAG Site resilient .

    Thanks

  50. Karthik says

    Hi Paul,

    I Have a scenario where i have three mailbox servers, and five databases divide on the basis of the employee roles.
    1.If i want to configure DAG for all the five database, can i create 5 DAG’s?
    2. Can a single mailbox server be part of multiple DAG’s.
    3. All the databases are not on same Mailbox servers. Divided among three
    4. Each database is of 2TB size.

    • says

      Each server can only be a member of one DAG. In your situation I would create one DAG, and add copies of each database to each DAG member.

      2TB is too large a database in my opinion – the main risk being recovery situations (eg how long it takes to restore the entire database just to be able to restore a single mailbox/item, or how long it would take to reseed a database that large).

      I am for 200-300Gb as an ideal size, for those reasons.

  51. Basel says

    Thank you Paul for this greate learning document.
    A quick question though, How is the location (Hard drive and folders for DBs and Logs) will be determined in the secondary mailbox server (EX-2) when creating a DB copy?
    How can I let the DB copy be created in E:\maildb and logs in F:\Logs ?

  52. Alexandre Bouffard says

    Hi Paul,
    I have been using many of your Exchange post because they are very clear and helpfull.

    I have an issue with my DAG when comes the time to switch from database and it only happen with the second Exchange server when it database become the primary. The users lose their connexion briefly and are prompt to login again. That login will then prompt again a few minutes later like the Outlook client wasn’t able to keep the connexion to exchange. When I move back the database residing on the first exchange server everything comes back to normal. One thing I can see by comparring this tutorial with my installation is that I only have one NIC card per server not 2. The complete setup reside on virtual servers 2008R2 using Exchange 2010 Sp2 roolout8.

    Any idea where I can look at ?

    Thank you

  53. Harsha Perera says

    Hi Paul,

    I have question regarding DAG replication. Is there any way to schedule the DAG replication across 2 sites?

    Thanks

    • says

      Database replication in a DAG is a continuous process. There is no scheduling option.

      While replication can be suspended/resumed, those actions are not intended to be used as a scheduling function.

  54. Harsha Perera says

    Hi Paul,

    Thanks for your quick response.

    We are having DAG enviornment & connected to a remote site using a WAN link (MPLS). We feel our WAN link is totally consuming for replication. Is it ok if we pause the replication during day time & resume in the night time. What is the best practise to do a replication over the WAN?

    Thanks.

  55. Virendra Singh says

    HI..i am beginner in Exchange Server.I have one exchange Server 2010.Now i want to configure DAG for this production Exchange Server.

  56. Tarek says

    Hello Paul,

    My dag stopped updating the RpcClientAccessServer following a failover, I am having to manually update it now. Any idea what may be the cause of this?

    Thanks
    Tarek

  57. Rob says

    Hi Paul,

    Thank you, this is a really useful tutorial. May I ask a question? We have two DAGS – our live environment is on two servers, and the new DAG on four servers is soon going to be used. However, some new users are being created on the new DAG and we don’t want this happening yet. Is there an easy solution to this?

    Thanks in anticipation.
    Rob.

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